Discoveries – Weather – Discover-Nature

Heat Effects

The midwestern United States is experiencing a heat dome this week. This is the result of a high pressure system hundreds of miles across and moving very slowly. Air in the upper atmosphere of a heat dome is already warm, but is still cooler than the air below, and cooler sir sinks towards the Earth’s surface. As the air moves downward, it compresses air molecules together releasing heat, making the lower layers even hotter and drying out the area as moisture evaporates. With little or no moisture, no clouds form to relieve the heat and dry conditions.

^{Heat Dome over Eastern US by National Weather Service, Jun 26 2025}

Humans have a variety of ways to cope with high heat including being less active, drinking plenty of fluids, and remaining in shady or air-conditioned areas. Wildlife still has to get food and water every day and may have fewer opportunities available to them to avoid the high heat. Let’s look at how the heat is affecting a few of the backyard species common in the Midwest.

^{Photinus pyralis, Big Dipper firefly by Terry Priest}

Fireflies are cold-blooded, or ectothermic, and prefer warm and humid areas. They come out in the early evening and as their bodies warm, they become more active, flying and flashing more frequently, communicating with other fireflies to find a mate. Eggs are laid soon after mating, but these will perish if they do not remain hydrated. Turning off outdoor lighting for a few hours in the evening and maintaining taller, well-watered vegetation will help fireflies during hot and dry conditions.

^{American Toad by Brad Carlson, Mar 2012; and Bullfrog at Waterfall Place by DonArnold, 2022}

Frogs and toads are also ectothermic and require heat from the environment to live. Species worldwide, including American toads and bullfrogs in our area, find temperatures in the 70s to be ideal. As temperatures move into the mid-80s, these species and others are prone to dehydration and heat stress. In addition, they normally look for shady and humid areas to regulate their body temperatures, but the lack of moisture in a heat dome does not make those niches easy to locate. Maintaining shady, well-watered areas of the garden provides refuge for many amphibian species.

^{Cardinal looking to stay in the shade by Don Arnold, 2023}

Birds are often affected by extreme heat. Most birds have lower body temperatures than the outside air. This allows birds to easily dissipate heat from high energy activities, such as flight. Once the outside air gets above a hundred degrees, birds cannot lose heat to the atmosphere and become severely compromised by heat and dehydration. Rapid open-mouthed breathing, changing eating times to early or late in the day, sitting with wings outstretched, or exhibiting poor balance are all signs of heat stress in birds. Providing shady, undisturbed areas and readily available water sources gives birds the opportunity to move around less and stay hydrated.

Wild animals have to deal with weather extremes just as we do. Come to the Jurica-Suchy Nature Museum or a nature center near you to learn more about providing opportunities for wildlife to survive heat, drought, and other environmental conditions.

Insects Over Winter

It is starting to get chilly in the Midwest as we head toward winter. Insects also recognize the shorter daylight hours and dropping temperatures. They use two main strategies to cope with winters: freeze avoidance and freeze tolerance. Avoidance may require travel or a dry place to stay warm. Tolerant insects can stay here and control their body’s response to freezing temperatures. Staying in place has several advantages including being able to emerge early in spring, allowing those insects to feed before predators are out.

^{Clockwise from upper left: Monarch butterflies on migration by Dopeyden, Getty Images; Cecropia moth cocoon by Sylvie Bouchard, Getty Images; Milkweed bugs by Rick Wood, Rick Wood’s Images; Four-lined plant bug, Poecilocapsus lineatus, by Heather Broccard-Bell, Getty Images Signature; Common pill-bug by Ines Carrara, Getty Images}

Those insect groups that opt for traveling to warmer climates often make a one-way trip. Monarchs are one of the best known insect migrators. Monarchs east of the Rocky Mountains leave in early fall to arrive at overwintering sites in the mountains of Mexico. Their offspring return to the southern U.S. in spring to breed, and this second generation returns to the East and Midwest over the following summer. Monarchs west of the Rockies overwinter in Baja, California, and many of the same individuals that fly south do return, but their trip is considerably shorter allowing time for breeding during summer months in the northwest U.S.

^{Honeybees in hive by OK-Photography, Getty Images}

Many different species of insects can control or stop ice formation in their bodies. Honeybees cluster together and shiver, generating enough body heat to keep the air above freezing in their hive. Other insects get rid of all the food and water in their bodies, becoming dehydrated and unable to freeze. Some species can control where ice crystals may form in their bodies, and prevent their formation inside cells that would cause harm to the insect. Insect species that retain some water use cryoprotectants, chemicals resulting from large amounts of sugar. One such chemical is glycerol, which lowers the freezing temperature of water and other liquids.

^{Dragonfly larva with fish by Mauribo, Getty Images Signature}

^{Fast running stream by Mburnham, Getty Images}

Some insects remain active throughout the winter. Aquatic insects in immature stages can easily spend the winter in fast moving or deeper water that does not freeze. Some insects move inside warm and protected places like attics, sheds, and gaps in house walls. They also overwinter in tree cavities, under bark, inside dead plants, and in old burrows. Allowing vegetation with hollow stems to stand through the winter will provide many populations a safe place to spend the season.

The insect version of hibernation is called diapause, when growth and development is halted until longer daylight hours prevail. Late winter weather patterns with warm periods interspersed with cold periods endanger many species. Another change we have experienced in recent years involves warm temperatures lasting later in fall and starting earlier in spring. These changes interrupt the historical natural cycles, causing insects and other animals to abort hibernation and actively look for food or mates. Food plants do not produce enough to support animal populations, or another cold period returns, and species are not able to adapt, and often perish.

^{A garden in winter by Vermontalm, Getty Images; Snag and deadwood in winter by BayDavn0211, Getty Images; Spring garden and returning insects by Anthony Lerma, Getty Images}

Insects are a vital part of healthy habitats, providing pollination services and food to many species. We can help overwintering insects by leaving dead stalks standing until late spring to provide safe habitat. Leaves left piled up provide nutrients, insulation, and a place of shelter. Uncovered soil can also host ground nesters such as native bees. Snags and logs provide lots of cavities protected from the weather. Selecting some plant species that bloom early or late in the year will provide additional food at those times. Growing plants in clusters enables insects to find all they need in one place. With a little planning, everyone’s backyard can be an inviting habitat for insects year-round.

Tornado

Springtime in the Midwestern United States brings with it everything from light to heavy showers, including tornados. In Illinois, we see an average of 54 tornados a year, with most of them occurring in the month of May. Tornados also occur in other parts of the world during springtime, including Europe, eastern and western China, South Africa, southern Brazil and both the east and west coasts of Australia, but not as frequently as in the U.S.

A majority of storm fronts move from southwest to northeast, which is a contributing factor in the Midwest to the formation of violent storms. There are three types of tornados. Non super-cell tornados are small, narrow, and last for only short periods of time, usually only a few minutes. Wind speeds are low, topping out near 80 mph, capable of causing only minor damage. Squall line tornados are generated by smaller thunderstorms traveling one after another forming periods of rain interspersed with calmer conditions. As the end of a squall line bends, small tornados may form with lower wind speeds, usually causing no damage. Super cell thunderstorms are the largest, most powerful storms that can generate tornados ranging from small to great in size and intensity.

^{Upper left: Thunderstorm during VORTEX2 by Sean Waugh, NOAA-NSSL Lower left: Funnel cloud approaching the ground by National Severe Storms Laboratory, NOAA Right: Supercell often associated with violent weather by National Severe Storms Laboratory, NOAA}

Rainstorms form when cool, dry air overlays a layer of warm, moist air. As the warm air rises to higher altitudes, where there is less air pressure, it expands and cools, losing its ability to hold moisture. As water condenses from the cooling air mass, water vapor floating on the air forms clouds. As more warm, moisture laden air moves into the system, the water vapor droplets become heavy enough to fall as rain. As rain falls, it cools the lower air layer, reducing the warm air flow until the rain stops.

^{Photomontage of the evolution of a tornado : Composite of eight images shot in two sequences as a tornado formed north of Minneola, Kansas on May 24, 2016, by Jason Weingart}

Thunderstorms form in the Midwest from warm, moist air moving in from the Gulf of Mexico and cool, dry air blowing in over the Rocky Mountains. A third source of air from the jet stream may wick away enough rain drops so that the lower air mass does not cool, and the warm air keeps feeding and intensifying a storm. As air moves in different directions and at different speeds, the whole storm will start to swirl, tending to pick up speed toward the center of the storm, eventually creating one or more funnels of rotating air.

Tornados are categorized based on the Enhanced Fujita scale from EF-0 to EF-5. This scale gives an estimate of wind speed and severity of damage inflicted. A little more than half of all tornados are found in the EF-0 range where wind speeds do not exceed 85 mph (137 kph) and damage is minor. Less than 1% of all tornados are recorded in the EF-4 (winds 166-200 mph) and EF-5 (winds over 200 mph) ranges. Another recent discovery is that most of the more severe storms tend to produce multiple tornados rotating around each other. Occurrences of multiple small funnels are difficult to observe within a large and often opaque mass of water, wind, and debris. This discovery helps to explain damages where one house may be completely destroyed while the neighbor is almost untouched.

The afternoon is the most likely time of day for these conditions to exist, once the sun has had a chance to heat the earth and air masses in the lower altitudes. In the Midwest, most tornados occur between noon and 8:00pm. Weather services are constantly monitoring conditions to be able to identify when weather patterns exist that may result in the formation of a tornado. Outside warning sirens are used by many municipalities to let people know that dangerous conditions are imminent. If you are hearing a warning siren, move inside and stay away from windows. Tune into radio, television, or internet resources to obtain the most up-to-date information for your area.

Beat The Heat

This week, the weather has been hot for the upper Midwestern U.S. with temperatures topping out above 100°F. Combined with high dew points in the mid-70s, the heat index temperature was upwards of 110°F. Here are some ways that plants and animals keep cool in the extreme heat.

^{Mojave Desert by LezusRocks, Getty Images}

^{Kit fox at entrance to desert den by Stevelenzphoto, Getty Images}

Desert environments, where hot conditions exist daily, are home to numerous animal species that live underground. Heat from the sun penetrates soils and sand layers for several inches, but at 20″ below the surface of the sand in the Mojave Desert, temperatures are fairly constant around 86°F while the surface may be over 110°F. Few large mammals are known to use burrows, although kit foxes and humans are two examples. Basements and lower levels in buildings are often preferred areas on hotter days.

^{Shaded walk in the woods by Felixmizioznikov, Getty Images}

Shade from trees is highly effective in creating cooler areas. Leaves are lighter in color than most soils and paved areas, and leaves reflect much of the sun’s radiation upwards, away from the shady area underneath. Denser foliage and rough leaf textures enhance the cooling effect. Under a shade tree, temperatures may drop up to ten degrees and other surfaces no longer exposed to direct sunlight, including our skin, may be 20 to 40 degrees cooler.

^{African elephant by Petr Polak, Getty Images: Black-tailed jackrabbit by Rancho_Runner, Getty Images; Fennec fox by Nattanan726, Getty Images}

Vasodilation occurs when blood vessels near the skin’s surface expand so more blood flows next to the skin. Many animals living in hotter climates, including fennec foxes, black-tailed jackrabbits, and African elephants, have large ears with broad, flat surfaces devoid of hair, fur, or other insulation. The ear’s large surface area is covered by a thin layer of skin and blood vessels. During hot weather, heat carried in the blood through the ear is readily lost to the outside environment, providing a cooling effect for the rest of the body.

^{Large crowd by Shaunl, Getty Images Signature}

Evaporative cooling is another method through which heat can be dissipated from a body. Trees use this method by losing water vapor through their leaves during photosynthesis, cooling the air under the leaves. Humans employ this method in a process called sweating. We lose warm water through skin pores directly to the air around us. Sweating also moistens our skin’s surface, indirectly providing additional cooling as air moves across the skins surface and wicks away additional heat. An important aspect enhancing the effectiveness of this method is our posture. Being supported by two legs, rather than four, exposes much less surface area to the direct rays of the sun, and much more surface area to air currents.

^{Forest path by Inga Nielsen, Getty Images}

While sweating is good for cooling, it is removing water from the body, which must be replaced for the process to continue. Exposure to today’s temperature extremes may result in a loss of three gallons of water or more from an average-sized human. As you are out enjoying nature during hot days, remember to keep hydrating to stay cool and keep other bodily systems healthy.

Boreal Forest in Winter

The boreal forest is the largest tract of woodland on earth covering 11% of all land area, half again as large as the Amazon rainforest. It stores 30% of the sequestered carbon on earth. The area also contains a mosaic of wet meadows, ponds, lakes, marshes, and bogs interlaced among the trees. Tree species include many conifers, dominated by spruce, plus aspen, birch, willow and alder. The animal life is abundant, with every species that was there before European settlement still remaining.

^{Boreal Forest panorama by Mliberra, getty Images}

The boreal forest is distinguished by short, hot, wet summers and long, dry, cold winters. When the last glaciers retreated northward, many holes and fissures were left behind. As the ice melted, all of these depressions were filled with water. The underlying geology is mostly granite shield, a rock layer that holds the water in and contains few minerals that dissolve in water, yielding very clear water that does not promote algae or bacteria growth. Most lake life is found in the shallow, warmer edges which also provide support to nearly all of the land-based fauna.

^{From upper left clockwise: Alder tree by Mantonature, Getty Images Signature; Spruce trees by Hannu Koskela, Getty Images; Willow tree by smarko , Pixabay; Aspen trees by Adamisovitsch, Getty Images}

Winter time presents many challenges including less sunlight, colder temperatures, less available water, less food and shelter, and increased severe storms. Animals that are active daily have higher energy requirements in winter. They must often change their dietary sources to whatever is available in winter. Grey squirrels and beavers cache food during warmer periods. Birds eat foods higher in calories such as nuts, seeds, dried fruit, and insects found under tree bark. When changes are consistent from year to year, species develop adaptations to meet the requirements of each season and are able to live comfortably throughout the year.

Shelter becomes not only a place to hide from predators, but also provides protection from weather extremes. Snow of different thicknesses and weight covers the landscape. Snow is also a great insulator, keeping cold winds away from exposed skin. There is normally a layer of air between the ground and the snow cover immediately above. Temperatures in this space are warmer than the exposed air above the snow creating a winter habitat that is vitally important for many species. Mice and voles create burrows under the snow where they can huddle together for added warmth. Similarly, air pockets surrounded by a heavy growth of conifer needles create spaces above the snow cover for birds and some larger mammals to shelter. And many larger species will nestle into the snow pack to shelter from storms and wind.

^{Spruce grouse by Impr2003, Getty Images}

^{Willow ptarmigan by Alex Berger, Mar 2022}

Spruce grouse, Canachites canadensis, and willow ptarmigan, Lagopus lagopus, are not able to fly more than several yards. They grow feathers on their feet to insulate them and aid in traction. Grouse use the air layer at ground level to shelter in.

^{Portrait of a snowshoe hare by Jim Cumming, Getty Images}

^{Canada lynx by Carol Gray, Getty Images}

Ptarmigan, along with snowshoe hares, Lepus americanus, and short-tailed weasels, Mustela erminea, all change color to pure white to hide from predators. Snowshoe hare and Canada lynx, Lynx canadensis, have very large feet that aid in walking on snow without sinking in. Arctic fox, Vulpes lagopus, are winter specialists with compact bodies and short legs and ears that limit their exposure to cold, and large, furry paws that enable them to walk on top of the snowpack. With their long, bushy tails wrapped around their heads, they can withstand winds and temperatures to fifty below zero.

^{Stayin’ warm, Arctic fox by PEDRE, Getty Images Signature}

You can learn more about this cold but wondrous habitat by searching online for boreal forest, referring to the southern portions of the habitat, or taiga, referring to the northern portions. Also, look for information concerning seasonal adaptations for species in your own area, or visit a local natural history museum such as the Jurica-Suchy Nature Museum in Lisle, Illinois.

A Spring Walk

The weather has included a lot of rain in these past few days, and there is more coming. Temperatures are still cool at night, but getting quite warm during the day, contributing to unstable air, thunderstorms, and tornado watches. Vegetation in our area is green and lush, inviting for the many species that inhabit our area. I hope you enjoy the sounds and pictures of spring and some of the inviting observations we can look forward to in the near future.

Boreal chorus frogs, Pseudacris maculata, are still out calling, even though it is near the end of their breeding season.

by DonArnold 2022

Another early spring species, white trout lily, Erythronium albidum, is still blooming.

by DonArnold 2010

And now that warmer weather is here to stay, both eastern garter snakes, Thamnophis sirtalis, and plains garter snakes, Thamnophis radix, are moving away from their winter dens and dispersing into woods and fields.

Garters emerging from winter den by DonArnold 2021

Golden Alexanders, Zizia aurea, and celandine poppy, Stylophorum diphyllum, are making a bright yellow welcoming splash for the next several weeks.

Weather always plays a large role in late spring in northern Illinois. A good thunderstorm can bring wonderful, soaking rains or wind and lightning to drive us indoors.

Thunderheads are a weekly happening by DonArnold 1986

Many species depend on water in ephemeral ponds at this time of year, including frogs, toads and salamanders. First to call are chorus frogs, Pseudacris maculata, then gray tree frogs, Hyla versicolor, and finally bullfrogs, Lithobates catesbeianus, call well into summer.

Gray tree frogs calling by DonArnold 2022

Bullfrog at Waterfall Place by DonArnold 2020

As spring moves into early summer, look for wood ducks, Aix sponsa, in woodland ponds

by DonArnold 2012

And mallards, Anas platyrhynchos, with puffball babies keeping close to mama

by DonArnold 2020

Green dragons, Arisaema dracontium, and their close relative, Jack-In-The-Pulpit, Arisaema triphyllum, are already standing tall

Other species to begin to watch for in the coming weeks include bumblebees gathering pollen from flora of all species and Eastern black swallowtail caterpillars, Papilio polyxenes asterius, destined to fly away at summer’s end.

Bumblebee collecting rose pollen by DonArnold 2020

Eastern Black Swallowtail larvae on fennel by SueOBrien 2020

I hope you are able to observe these and many other sights in the coming weeks on your neighborhood walk or in local forest preserves.

Spring Rains

Rain gardens help control thunderstorm effects

Even though it is still spring on the calendar, temperatures are soaring, bringing big changes to the atmosphere and the air and water cycles. Water, mainly from our oceans, constantly evaporates into the air that is moving over the surface. Denser air fills the lower levels of the atmosphere and is able to absorb more water vapor and more heat. As an air mass warms, it rises and spreads out in higher levels of the atmosphere. Air becomes less dense, loses some of its heat, and allows water vapor to condense and form clouds. Most clouds do not have rainfall because the updraft of warm air is fast enough to keep the small water droplets forming the clouds from falling. Rain happens when enough water condenses to form a heavy enough droplet to fall.

Wyoming thunderstorm by Bill Lile, Nov 2008

As this process of rising and falling air and water droplets continue, a storm develops. Loss of heat also releases small electrical charges, which will eventually combine into a chain called lightening. Worldwide, about 2,000 thunderstorms are happening at any given moment. There are 100,000 annually in the U.S., and about 10% reach a severe level with hail, winds exceeding 57 mph, or spawning tornados. Rains can be heavy, putting down vast quantities of water on the landscape in a short period of time. How much water? One inch of rain on an acre equals 27,154 gallons of water. At Benedictine’s campus in Lisle, one inch of rainfall equals about 3 million gallons. On average, rainfall in the continental U.S. would cover every acre with 30″ of water annually.

Several storms sweep the northern US by NASA, Oct 2010

In the last century, worldwide average temperatures have risen 1.4˚F, and are expected to rise 3˚F to 5˚F in the coming 100 years. We are experiencing more rainstorms annually, and they are of greater intensities due to warmer air holding more water vapor and rising temperatures sucking more moisture from both land and ocean. When clouds condense enough to form rain, there is a greater quantity of water vapor, so rainfall is heavier from greater amounts of water falling back to earth.

Cloud formation by Dean Morley, Oct 2012

Heavier rainfalls may be absorbed in some areas, if they do not happen too often. However, most watersheds have been heavily affected by human activities including deforestation, dams, irrigation activities, depletion of groundwater, and draining of wetlands. More rainfall running off the surface leads to less moisture in the soil and allows soil to get hotter and drier. As rains ease toward midsummer, vegetative areas are harder hit by these dry effects.

Rain gardens are a simple and inexpensive way to alleviate some of these problems. They can be created in any area where the soil is slightly depressed. Runoff is directed into the area where it can soak into the ground. Many are planted with grasses or flowering native perennials providing a beautiful garden while reducing runoff. It is an easy solution you can create in your own backyard. For more ideas, click this link: for Rain Garden Requirements & Plant Lists from the Illinois Department of Natural Resources.

A Drought of Amphibians

This year we are experiencing drought conditions in northeast Illinois. A drought, defined as a period of little or no rain, can have major impacts on the amphibian populations of an area. At the end of winter, as snow melts and expected spring rainstorms move into the area, many ephemeral wetlands fill with water. These pools, marshes and ponds contain water for only short periods ranging from several weeks to a few months. But they are an important link in the chain of amphibian reproduction.

Many frogs and toads live in woodland areas, but depend on wetlands for breeding and habitat for their young. Male frogs and toads return to local ponds each spring to find a mate by calling. Most calling is done in the evening, but sometimes individuals call during the day. Females will find their way to their favorite singer, then lay a gelatinous egg sac, which the male fertilizes. Eggs may be located on floating vegetation, hanging under rocks or logs, or laid on the bottom. Eggs have no shell and must remain wet to live. Eggs hatch into tadpoles in a week or less. Tadpoles may transform to adult form in as little as two weeks or as long as the following year.

Wetlands of all types are showing changes due to the drought conditions. Shallow ponds and marsh areas are dry or retaining only enough moisture to have wet soil, and are no longer a usable wetland for many species. Deeper ponds are down several inches in depth. A difference of only a few inches in depth can add several feet of shoreline where banks gradually slope into the water. Exposed rocks and logs used by turtles for basking are high enough over the water’s surface that they may no longer be accessible to these species. Creeks and rivers are lower and slower. Turtles and water snakes that depend on depth and fast flow for protection may find these are no longer a means of escape.

Shrinking permanent wetlands put pressure on the species that already live there. Ponds are habitat for newts, tadpoles, crustaceans, frogs, toads, turtles, birds, naiads and insects, and microscopic life. As the amount of water decreases, habitat in the pond is reduced. Shallows where a bank slowly submerges may have a steeper drop-off. Logs once laying at surface level may be several inches higher than the surface, eliminating areas underneath, once used for protection. Less water means less available oxygen and food for the animals already sharing the pool. Den and nest sites in banks at the water’s edge become more exposed.

Rain during the early part of May has helped alleviate some of these issues, but more rain is needed, continuing into the summer. Maintaining your own backyard wet areas with shade and consistent watering provides good habitat for many animals that live among us. You can watch many of these species in area wetlands on trails and in local parks this spring.

Tornado

April in Illinois sees more tornados than any other month, although the peak season will last through June. Tornados form mostly in the late afternoon or early evening, after the sun has had time to heat the atmosphere. About 54 occur yearly in Illinois, with more than half of them coming during the next three months as the jet stream centers over our latitudes.

Tornados develop over several hours. First there is a thunderstorm where a warm, moist air mass is located in front of an eastward moving cold front. The cold air pushes up and over the warm air creating instability in the air mass. Warm air pushes upward and cools as it reaches higher altitudes. As the air cools, moisture carried aloft in the warm air condenses to form water droplets that fall back toward the warmer air. This area, where air continues to rise and fall, is called a convection cell. With small amounts of air and water, clouds will form; with large amounts, a thunderstorm may develop.

Wind at varying heights, moving in different directions and speeds, can start a rotating column of air. As warm air is drawn into the bottom of the column, rotation speed increases, becoming faster toward the higher regions. If the air in the rotating column near the ground is very cold, it will spread away from the storm and a tornado will not form. Once a tornado is spawned, it may persist for only a few seconds or for several hours. Tornados move about 30 miles per hour and generally cover less than six miles. There are an average of 100,000 thunderstorms occurring in the U.S. annually, spawning about 1,000 tornados. Damage from these storms is caused by the high winds as well as flying debris.

NOAA-NASA Storm Tracking over midwest US

A variety of scientific instruments are used to detect when and where tornados will form including satellites, weather balloons, radar and computer modeling. The first time radar detected a tornado was in 1953 in Champaign, IL, while running tests on a new radar site. This led to a push to create a nationwide network of radar sites for tracking dangerous weather related events. In the 1990s, a new radar system was created that was able to track the Doppler Effect which shows a change in the frequency of a sound wave as the source of the sound is moving in relation to the radar site. Doppler Radar can detect areas of rotating air within a thunderstorm, and rotational speed, providing more precise information for forecasters trying to determine if a tornado will form.

How Radar Works at weather.gov/jetstream/how by NWS

Being prepared is the key to staying safe and reducing the risks from these natural events. Pay attention to weather reports, warnings, and watches. At home, know where safe shelter is located. Whether home or away, tune to NOAA Weather Radio or follow instructions from local officials. If your community has sirens, become familiar with the warning tones. When outside, do not trust bridges – you are safer in a low, flat location. Be aware of flying debris, and use your arms to protect your head and neck. At home, move to a basement or small interior room away from windows, doors, and outside walls. Remember to include pets in your plans. You may consider storing emergency supplies including water, non-perishable foods, medical supplies and medication.

There have been numerous studies and statistical analyses done on tornado events. In the past 70 years, there has been no real increases in number of tornados occurring annually. Due to better data collection techniques, historical records show sharp increases in the number of recorded tornados occurring twice, first in 1954, after the new countrywide radar network was activated and in the mid-1990s after Doppler Radar was put into general use. More information is available at the Illinois State Climatologist’s website including maps of previous events for each county at IL Tornado Mapping and plots of tornado related statistics at IL Tornado Plots.

Hibernation

Days are getting shorter and temperatures are starting to cool. We are well into autumn, and it is time for animals to prepare for winter when it will become difficult for them to keep warm and find food. There are several approaches to living through winter: growing thicker fur coats, travelling south to follow the quickly retreating warmer temperatures, and sleeping in until warmer, sunlit mornings prevail. Animals that “sleep-in” are actually going through a period of dormancy. It can last from a few weeks to several months, but there are some general conditions that must be met. Almost all species will need a home that consistently stays above freezing, and each animal must have enough energy to last through the dormancy period. There are four categories of dormancy including hibernation, torpor, brumation, and diapause. Let’s take a look at these methods and some species that use each.

Hibernation is a process that involves a significantly lower body temperature, and decreased heart, respiration, and metabolic rates. Species that are true hibernators can live for long periods of time with very low energy use. Woodchucks, also known as groundhogs, hibernate up to five months each year in the northern areas of the eastern U.S. They have a normal heartbeat of 80 beats per minute which is reduced to about 5 beats per minute; their normal body temperature is reduced from 98°F to 38°F; and their breathing rate goes from 16 times per minute to twice a minute. The woodchuck also exhibits reductions in other growth areas including teeth, which normally grow 1/16″ weekly and are kept under control by the grinding action when they eat.

Eatern Chipmunk, *Tamias striatus*, by DonArnold, c-1999

Species are either obligate or facultative hibernators depending on when they enter a period of dormancy. Obligate hibernators use seasonal cues. When days start to shorten, indicating a change in season, these species will enter hibernation regardless of outside temperatures or amount of available food. Facultative hibernators use environmental cues. When it becomes too cold or food starts to become scarce, these species will enter hibernation to conserve on their energy use. All species that spend time in hibernation eat larger amounts of food in autumn to build up brown fat. These fat reserves provide the quick energy needed for activities upon awakening.

Species in hibernation may waken occasionally. Animals have been observed waking to use a toilet area and/or to nibble on cached food supplies. Chipmunks can be observed with fat cheeks in autumn, busily creating food caches located in burrows found under the frost line in the same area where their summer nest is located. Although this reason for waking is not well understood, one theory is that waking may stimulate energy use followed by the ability to sustain a longer sleep period. Another theory postulates that periodic eating of small amounts of food sustains the immune response system.

Torpor is a similar process that involves the same physical modifications as hibernation, but in smaller quantities. Body temperatures and heart rates will be lower by ten to fifteen percent, and animals using this strategy will wake more often, engaging in activities several times throughout the cold period. Skunks enter their dens as daytime temperatures sink below freezing, and their heart and respiration rates slow. Their sleep may last from a few days to a few weeks. They will leave the den to forage for food in between these naps. Many birds enter torpor on a daily basis, at night or on very cold days. Their decreased physiological activity allows them to conserve body fat overnight so it is available for quick energy production the following morning to continue daily foraging activities. On cold nights, black-capped chickadees can maintain body temperatures twelve degrees lower than normal. This allows the body to use 30% less stored fat.

Brumation is the term used for torpor in ectotherms. Ectotherms obtain their body heat from the environment and include reptiles, amphibians and fish. Most of these species must live where the temperatures always stay above freezing. Many frogs and turtles bury themselves in mud at the bottoms of ponds, or dig holes deep into the ground, well below the frostline. Their breathing and heart rate slow and they can get oxygen from air trapped in the cavity or surrounding mud. Snakes will often den together in groups of a dozen to several hundred individuals in a den below the frostline. The wood frog is an exception because it can tolerate freezing temperatures. A chemical contained in each cell in its body acts as antifreeze to protect the cell from damage that could be incurred if solid ice should form inside the body. Thirty five to forty five percent of the body may freeze, stopping the heart and respiration, but it will thaw with warming temperatures. The wood frog may freeze and thaw several times in one season. All ectotherms may wake on warmer days in mid-winter and leave their dens to find water and nutrients.

Yellow-Jacket Wasp by Dog-WalkDigital, c-2011

In late autumn, before temperatures turn cold, some insect species enter diapause, a period of suspended development. Some spend winter here in underground burrows, under bark or leaf litter, or in holes drilled into woody plants. Many have the same cellular chemistry as wood frogs, with each cell having a chemical antifreeze to prevent damage from ice formation. For bumblebees and yellow jacket wasps, only the new queens survive, spending the winter in an underground burrow until spring. Bees spend the longest time in any form of hibernation, often five to six months underground.

Strategies to survive cold periods are important as parts of the normal annual cycle. Zoos attempt to provide habitat that can accommodate these needs. Cold-adapted animals in northern climates remain outdoors for winter as part of a healthy life cycle. The risks involved with cold periods include the need to meet nutrient demands by storing fat or food caches, having energy in reserve to forage when warm weather arrives, and having enough water to hydrate throughout the cold period. Climate change and warm days in the middle of winter are another threat that is not easily quantifiable. Animals may wake and start to move about during warming episodes, but may not find any food available, wasting energy and water.

We can help by following some simple guidelines: leave animals and habitats undisturbed during cold months; offer food sources for animals during warmer periods (i.e. extra seed if temperatures get above freezing); learn more about the habitats in your neighborhood to protect them from disturbance and fragmentation and learn more about climate change and the negative effects caused by it. Here are a few books you may find interesting: “Animals That Hibernate”, a children’s pictorial by Larry Dane Brimner; “Do Not Disturb”, a children’s reader by Margery Facklam; “Winter World” by Heinrich Bernd.

Clouds

As I sit outside and watch all those gray and white dragons and trains float by, I wonder what makes up a cloud, as they billow and move lazily past me, forever changing shape. As we observe clouds, they provide weather information, shade, moisture, and sometimes entertainment.

Hole-punch altocumulus cloud, by DonArnold

Clouds are made from water and particles of both organic and inorganic matter. These may include dust, pollen, soot, and smoke. Humidity is the amount of water vapor present in the air. Air can hold a certain amount of water at any given temperature and warmer air can hold more water than cooler air. When the temperature reaches the point where the air is 100% saturated, the water condenses onto these particles. When massed together by the billions, the particles and water together form clouds. The droplets are so small that they are kept aloft by air turbulence and wind.

Clouds come in many shapes and are found at different levels in the atmosphere. Basic cloud types include cumulus, stratus, and cirrus. Cumulus clouds are dense, fluffy piles with rounded tops usually formed from the rising of warm over cooler air. Stratus clouds appear as a flat and featureless blanket or sheet, in varying shades of gray from nearly white to very dark. Cirrus clouds, found at very high altitudes, are made of ice crystals, appearing as narrow bands or thin, feathery patches.

Cloud names may be combined to describe additional characteristics. Cirrostratus clouds appear as several layers of narrow bands, while stratocumulus clouds appear as many fluffy forms compressed together into a large sheet of clouds. Prefixes added to cloud names include alto signifying middle level altitudes, and nimbo or nimbus signifying clouds with precipitation.

In Illinois, we average 167 days each year with some type of cloud in the sky. We can tell quite a bit about the immediate weather by simply looking at the clouds. Cirrus clouds are an indicator of fair weather. If cirrus clouds are getting thicker, this indicates that a warm front is approaching, bringing the possibility of precipitation, followed by clearing skies and warming temperatures. Stratus clouds are associated with overcast skies and relatively stable air masses. They may form fog or light precipitation, but are not associated with heavier storms. Cumulus clouds that do not grow very tall are an indication of fair weather. But, if cumulus clouds should start to grow, the atmosphere is unstable and pushing those droplets to greater heights. This may lead to light or heavy rain depending on the growth rates and heights of the clouds. Altocumulus clouds in the morning may well lead to precipitation in the later parts of the day or evening.

There is an average of 2,000,000,000,000 (two trillion) gallons of water in the atmosphere over Illinois at any given moment, and clouds may return this water to the ground in several different forms of precipitation. Rain is liquid water formed as droplets between 1/10″ and 1/4″ in diameter. Snow is when water vapor freezes inside a cloud into a crystalline form and falls through a cold air mass. Sleet is formed when snow from a higher, colder altitude, falls through a warm layer of air, turning to liquid rain followed by a cold layer near the surface refreezing the water into small ice crystals. Freezing rain falls as liquid water, but lands on a surface that is cold enough to have the rain drops freeze into ice as they hit. Hail is made from many layers of ice that accumulate on a falling particle. As the particle falls through each layer of atmospheric clouds, more water attaches and freezes to form each layer of ice.

Most clouds form in upper layers of the atmosphere, but fog is also a type of cloud. It forms when the air temperature immediately above ground level falls to the dew point temperature, and water vapor condenses on any particles in that air mass. Fog usually forms when there is little or no movement of air at ground level, or it quickly dissipates. Fog can create a surreal, almost magical scene, while at the same time conditions may become quite dangerous depending on where the fog appears and its density.

Stratus clouds, rain&rainbow, by DonArnold

Clouds can also make fantastic art and can spur our imagination. Artists throughout the past several hundred years have painted and photographed many varying forms providing character and depth to many works of art. There are even artists today who create real clouds indoors for our fascination and enjoyment. Take some time and get outside yourself to observe this wonderful imagination-inspiring scientific phenomena.

DewDew Dew-Dah

How’s the weather outside today? Are you feeling a little warmer than you would like? Have you seen the weather forecast, and do you really know what all those numbers mean?

The simplest is temperature which is a measurement of the heat content of the air. The two popular scales are Celsius and Fahrenheit. Both have two defined points: the freezing point of fresh water at sea level is 0°C / 32°F, and the boiling point of fresh water at sea level is 100°C / 212°F. Note that the Fahrenheit scale, created in 1724 based on experiments carried out at that time by Polish physicist Danielle Gabriel Fahrenheit, is commonly used today in only four countries including Belize, Myanamar, Liberia and the United States, and only for non-scientific applications.

Another popular number shown on most weather predictions is either heat index or wind chill. If the apparent temperature, the “it-feels-like” number, is higher than the actual temperature, it is shown as heat index; if it is lower, it is shown as wind chill. The heat index is derived from temperature and relative humidity and indicates heat gained between the human body and the atmosphere. The wind chill is derived from temperature and wind speed and indicates heat lost between the human body and the atmosphere.

The human body removes heat by perspiring and letting drier air wick heat away. When the relative humidity is high enough that perspiration does not evaporate, then there is no cooling effect. The human body begins to absorb heat from the atmosphere and is in danger of suffering a heat related illness. As heat or relative humidity rises, the combination becomes more dangerous. The National Weather Service has published the heat index shown here:

The wind chill index is derived from temperature and wind speed, and indicates heat lost between the human body and the atmosphere. Wind chill formulas vary greatly worldwide, but since 2001, the U.S., Canada and the U.K. have agreed on a standardized formula that uses the following assumptions: the wind is striking a bare face on a person walking 3mph into a 3mph headwind at an actual temperature of 10°C / 50°F or lower. As the actual temperature falls or the wind speed rises, the wind chill falls and the danger of a cold related illness increases. The National Weather Service has published the wind chill index shown here:

When reading a weather report, humidity and relative humidity are two terms often used interchangeably. However, humidity, properly called absolute humidity and expressed in grams, is the amount of water vapor, by weight, in a cubic meter of air. This measurement is rarely used outside of scientific experiments. Another term is dew point temperature, a number that is considered by most meteorologists to be a better indicator of moisture in the air than relative humidity.

Relative humidity is the amount of water vapor in the air relative to the maximum amount of water vapor that air can hold at a given temperature. As the temperature rises but the water content remains the same, relative humidity drops because warmer air can hold more water vapor than cooler air. This means that if the air temperature is 80°F at noon and 84°F at 2:00 pm, but the water vapor content is constant, relative humidity will be lower at 2:00 pm even though the air is not any drier. And what we “feel” is the actual amount of moisture, i.e. the absolute humidity, in the air. So, while the relative humidity is dropping, it does not “feel” more comfortable.

The dew point temperature is also an indicator of how much water vapor is in the air, as well as how it “feels” to us. Dew point is calculated by the use of a hygrometer, a polished metal mirror that is cooled until water vapor in the air starts to condense on the surface. The temperature when condensation first starts is the dew point temperature.

When the outside air temperature cools down to where it is the same as the dew point, water condenses to form fog at surface levels, clouds at levels aloft, or a film of dew on surfaces. The larger the spread between temperature and dew point, the more comfortable we feel because as the temperature rises and the dew point remains constant or falls, the air becomes drier.

Humidity can make you feel uncomfortable whether you are in shade or sun, whether it is windy or calm, or whether you are acclimated to heat or not. As the dew point gets higher and closer to the actual temperature, we start to feel that humidity; we start to feel ‘sticky’. Remember, a person gets cool by perspiring, and no matter what the actual temperature, we can only get cool when perspiration can evaporate which only happens when air is not already saturated. A dew point greater than 65 is uncomfortable to most people. Dew point temperatures above 70 indicate unstable air conditions that may lead to severe weather.

All of this and more is included in the science of biometeorology; the study of weather and its effects on the human body. I will look at additional aspects of this science in later columns. To locate these numbers, take a look at your favorite weather website, or try one of the following:

www.weather.com The Weather Channel Today, Hourly, 10-day Temp, clouds, wind speed & direction, chance of precip, heat index, windchill, humidity, UV index

www.accuweather.com Accuweather Hourly, Daily, Radar, Air Quality Temp, clouds, wind speed & direction, Humidity, UV, DP

www.wunderground.com Weather Underground Hourly, Daily, Historical Temp, clouds, wind speed & direction, chance of precip, heat index, windchill, humidity, DP, pressure

www.weather.gov National Weather Service / NOAA Current, Daily Forecast, History Temp, clouds, wind speed & direction, humidity, pressure, DP

www.weatherbug.com Weatherbug Current, Hourly, 10-day Temp, clouds, wind speed & direction, heat index, windchill, humidity, DP

https://www.wsdot.com/traffic/passes/snoqualmie/ Snoqualmie Current Weather My favorite ski area 🙂