Behind the Forecast: What is an ‘Extreme Heat Belt’

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Published: Aug. 19, 2022 at 9:21 AM EDT
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LOUISVILLE, Ky. (WAVE) - New research shows an “extreme heat belt” is developing across regions of the United States. But what does that mean?

The First Street Foundation report found that an area from Texas to Louisiana, stretching north to the Great Lakes (Illinois, Indiana, and Wisconsin), could see heat indices above 125° by 2053. These numbers are typically seen in Death Valley or the Middle East. More than 107 million people could be impacted over the next 30 years. Currently, only 8.1 million U.S. residents in 50 counties are under that risk.

The model used high-resolution land surface temperature measurements while incorporating the impacts of water proximity, tree cover, impervious surfaces (like concrete and asphalt), and other factors.

The model used in the report showed an increase in the number of days with a heat index over 100° across most of the country over the next three decades.

The National Weather Service defines a heat index as “a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.” Once the heat index exceeds 105° to 110°F for at least two consecutive days, the National Weather Service may issue heat alerts. The heat index measurement is only devised for shady conditions and light winds. Full sunshine can increase the heat index by up to 15°!

The WetBulb Globe Temperature (WBGT) is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle, and cloud cover (solar radiation). The Wet Bulb Temperature is procured from the combination of three different thermometers. A black globe thermometer is used for the solar factor (sun angle and cloud cover). The wet bulb measures the humidity while the dry bulb is used for the ambient temperature.

The National Oceanic and Atmospheric Administration’s data shows that July was the United State’s third hottest since records began 130 years ago.

This heat trend has significant ramifications, especially in terms of agriculture, water supply, and health. Heat is still the leading weather-related killer in the United States.