Has 2026 been an active tornado year?

Posted on August 10, 2026 by WeatherGuys Editor

A tornado is a violently rotating column of air that is in contact with both the surface of Earth and the storm above. The 30-year normal (1981-2010) for Wisconsin is 23 tornadoes per year.

The average number of tornadoes that occur in Wisconsin each month, based on data from 1991 to 2020. (Image credit: Wisconsin State Climatology Office)

As of mid-July, the National Weather Service has confirmed that our state has experienced 39 documented tornadoes, which ties it with 2025 for the 6th most tornadoes in an entire year. These tornadoes were distributed over 10 different days. Twenty-seven of those tornadoes were spawned between April 13 and April 17, with 16 on April 17 alone.

Given that we are still prone to such storms, by the end of the year it is likely that 2026 will be in the top five for number of tornadoes in Wisconsin in a year. The most tornadoes in a single year occurred in 2005, when 62 tornadoes hit the state.

Tornadoes are classified based on the damage they cause, and that damages enables an estimate of the speed of its rotating winds. All tornadoes are assigned a single number from the Enhanced Fujita, or EF, Scale, according to the most intense damage caused by the storm.

The strongest tornadoes in Wisconsin so far this year were three EF-3 tornadoes with wind speeds between 136 and 165 mph. They were in Union Center (Juneau County) on April 14, in Cream (Buffalo County) on April 17, and in Ringle (Marathon County) also on April 17. These tornadoes left ground trails of 7.3 miles, 10.4 miles and 13.5 miles, respectively, with a width of 600 yards.

An EF-2 (111-135 mph) was also observed on April 14 in Lisbon (Waukesha County). The remaining 2026 tornadoes were either at EF-0 (wind speeds between 65 and 85 mph) or EF-1 strength (86-110 mph).

Though they do vary in intensity, it is important to remember that tornadoes of all strengths can be destructive and potentially life-threatening.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on Wisconsin Public Radio at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: History, Seasons, Severe Weather

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What is atmospheric ducting?

Posted on August 3, 2026 by WeatherGuys Editor

Atmospheric ducting is a phenomenon that affects how radio waves travel through our atmosphere.

(a) Duct formed by cool air below warm air and (b) Duct
formed by cool air trapped between two layers of warm air. (Image credit: M. Banafaa, A. H. Muqaibel: Tropospheric Ducting: A Comprehensive Review)

Radio waves are a type of electromagnetic energy that carry information as they travel by modifying certain properties of the wave, like their amplitude or frequency. In a vacuum, radio waves travel at the speed of light. In Earth’s atmosphere, radio waves travel at very nearly the speed of light.

Radio waves move through the atmosphere, and their path can be a direct line or involve bending, reflection or scattering. Radio waves are used in various communication devices such as standard broadcast radio and television, navigation, the Emergency Alert System and NOAA Weather Radio. Radio signals are an essential mode of communication during emergency situations.

Atmospheric ducting occurs because of variations in the atmosphere, particularly temperature and humidity, causing radio waves to bend back toward Earth rather than to disperse into the atmosphere This allows the communication signals to travel long distances, sometimes unintentionally. Radio waves, or other electromagnetic signals, get trapped and guided along the duct. The duct is basically a tunnel that the radio waves bounce through until they eventually exit.

An interesting example of communication signals traveling a long distance occurred at 3 a.m. July 1, 2026. An outdoor severe weather emergency alarm in northeast Indiana was set off, even though there wasn’t any severe weather occurring or forecast anywhere for hundreds of miles. The siren was activated by radio signals all the way from Iowa, 300 miles to the west. Those radio signals accidentally matched the activation code of the siren in Indiana.

In early July, the Midwest was under a heat dome, and the atmospheric temperature and humidity structure allowed the radio signals to travel beyond their normal reach.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on Wisconsin Public Radio at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Meteorology, Phenomena

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Is wildfire season getting longer?

Posted on July 27, 2026 by WeatherGuys Editor

Wildfires are an important part of many ecosystems and an essential part of forest and rangeland health.

Fires require fuel to burn, heat to ignite and oxygen to burn. Wildfire season is defined as the time of year when wildfires are most likely to ignite and spread. A combination of high temperatures, low humidity, lack of precipitation days and high winds make wildfires more likely to spread and lengthen fire seasons.

Weather and climate are important in making fuel available by determining the moisture content of the vegetation. Since the weather and climate of a region play key roles in these required ingredients, fire season varies in timing and duration based on geographic location.

Wildfire season’s duration is increasing, as demonstrated by several scientifically documented trends. Studies show that fire seasons are lasting longer and that more acres are burning annually than in previous decades.

An analysis of 35 years of meteorological data by the U.S. Forest Service found that fire seasons are starting earlier in the spring and extending later into autumn. The National Interagency Fire Center has recorded the size and number of wildfires in the United States since 1983. Over the past 20 years, the amount of land area burned each year has increased as wildfires have grown larger, while the number of fires each year has remained fairly constant.

Many weather satellites can detect active wildfires from the heat signatures of the fires. Various weather satellites include observations to detect active fires. Using NASA satellites over the 21-year data span from Jan. 1, 2003, to Nov. 30, 2023, researchers found that extreme wildfires have become more frequent, more intense, and larger.

The satellites can also track the smoke produced during daylight hours. Smoke plumes are not detected at night nor in some cloudy areas. Smoke observations from satellites are useful in estimating air quality.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on Wisconsin Public Radio at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Meteorology, Severe Weather

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What is the wet-bulb temperature?

Posted on July 20, 2026 by WeatherGuys Editor

 The wet-bulb temperature is the lowest temperature to which unsaturated air can be cooled by evaporating liquid water into it.

The dry-bulb temperature is an indicator of heat content and is shown along the bottom axis of the psychrometric chart. Constant dry bulb temperatures appear as vertical lines in the psychrometric chart. Wet Bulb temperature can be measured by using a thermometer with the bulb wrapped in wet muslin, then exposed to the air flow. The Wet Bulb temperature is the temperature of adiabatic saturation. Lines of constant wet bulb temperatures run diagonally from the upper left to the lower right in the psychrometric chart. The adiabatic evaporation of water from the thermometer and the cooling effect is indicated by a “wet bulb temperature” lower than the “dry bulb temperature” in the air. Combining the dry bulb and wet bulb temperature in a psychrometric diagram or Mollier chart, gives the state of the humid air. (Image credit: weather.gov)

This may sound horribly obscure, but it serves as a very useful measure of human comfort. It combines atmospheric humidity and temperature in a way that helps determine our comfort level while in the shade, especially during hot and humid conditions.

Wet-bulb temperature is related to other humidity indicators such as dew point temperature. For example, at 100% relative humidity, the wet-bulb temperature is equal to air temperature. At lower humidity, the wet-bulb temperature is lower than air temperature due to evaporative cooling.

We determine wet-bulb temperature by using a thermometer that has a water-moistened cloth, or wet wick, wrapped around its bulb. The wet wick is connected to a water reservoir and then ventilated with ambient air. As air flows over the wet wick, water evaporates. Evaporation requires energy. As water evaporates from the wick, it absorbs heat from the surrounding air and the thermometer itself, lowering the temperature reading. After a few minutes, the temperature of the wet bulb stabilizes, and that temperature is the wetbulb temperature.

The world is getting hotter and there is a limit to how much heat our bodies can endure. Our body’s ability to cool itself relies on sweating and evaporative cooling. High wet-bulb temperatures indicate dangerous heat stress levels, as the body’s ability to cool itself becomes compromised when evaporation is limited. Exposure to a wet-bulb temperature of 95 degrees Fahrenheit (35 degrees Celsius) for longer than six hours is dangerous, as the human body cannot cool itself. Prolonged exposure to these conditions can become life-threatening.

The wet-bulb globe temperature is another heat stress index: It extends the wet bulb temperature by combining air temperature, humidity, radiant heat and wind to assess the risk of human heat exposure.

Steve Ackerman and Jonathan Martin, professors in the UWMadison department of atmospheric and oceanic sciences, are guests on Wisconsin Public radio at noon the last Monday of each month. send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Meteorology, Seasons

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Does NOAA conduct fire weather forecasting?

Posted on July 13, 2026 by WeatherGuys Editor

Wildfire outbreaks require the alignment of several factors, including temperature, humidity, winds and the lack of moisture in fuels such as trees, shrubs and grasses. These factors have strong direct or indirect ties to current weather, climate variability and climate change. The National Oceanic and Atmospheric Administration supports weather forecasting throughout a wildfire’s lifecycle: before, during and after the wildfire.

1-minute GOES-19 Shortwave Infrared images, with plots of Surface Wind barbs and Peak Wind Gusts (yellow/red) and Surface Fronts, from 1701 UTC on 17 February to 0100 UTC on 18 February. (Image credit: CIMSS Satellite Blog)

Drought conditions can set the stage for wildfires.

NOAA’s Climate Prediction Center provides seasonal temperature and precipitation predictions important to assessing fire risk. The National Center for Environmental Prediction, or NCEP, uses a suite of numerical weather prediction models to provide fire managers with actionable information on how near-term environmental conditions will influence fire risk, fire behavior and smoke impacts. These models provide temperature, humidity, wind, lightning and precipitation forecasts to aid in planning at the scale of days to a week.

During wildfire events, NOAA’s National Weather Service provides weather forecasts and interpretation services to help emergency personnel and public safety officials make decisions. Specially trained incident meteorologists, or IMETs, can be deployed to wildfire command centers, where they generate real-time fire weather forecasts to support firefighting operations. GOES and POES satellites are used to monitor wildfires and track smoke. High-resolution weather models are used to simulate how smoke will move and to predict its effects on weather, air quality and visibility.

Once the fire is extinguished, there may still be weather-related hazards. For example, communities below a burn scar face increased flooding threat. NWS forecasters closely monitor burn scars, using high-resolution weather models, satellite observations, Doppler radar and their knowledge of local terrain to identify when even modest rainstorms could produce a flooding threat.

Research shows that changes in climate are creating warmer and drier conditions, leading to longer and more active fire seasons in the western United States.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on Wisconsin Public Radio at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Seasons, Severe Weather, Weather Dangers

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