‘Heat Belt,’ which includes Ohio, to make extremely hot days more frequent, study says

MIAMI VALLEY — The frequency and intensity of extremely hot days could change over the next three decades because of our changing climate, according to new research from a Brooklyn, New York, research and technology group working to define America’s climate risk.

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Ohio will see higher temperatures over the next three decades, according to the non-profit group, First Street Foundation. Its model places seven Ohio counties inside a “Heat Belt,” which could develop from Texas all the way to southern Wisconsin that includes southwestern Ohio.

Butler, Clermont, Hamilton, Miami, Montgomery, Preble and Warren counties are included in the “Heat Belt.”

In this belt, the climate researchers say, there is the possibility of at least one day with a heat index of at least 125 degrees.

To see a heat index of 125 degrees in Dayton, our Storm Center 7 meteorologists took the hottest day on record -- 108 degrees set in 1901 -- and calculated the heat index using a dew point of 75. This could give the Miami Valley a 125-degree heat index value.

The heat index is a measure of how the air feels with the temperature and humidity combined.

According to First Street Foundations model, Butler County in the southern Miami Valley could go from seeing a heat index of 90 degrees or higher 55 to 76 times by year 2053.

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Temperatures above the threshold of the National Weather Service’s “extreme danger” category, when the heat index is more than 125 degrees Fahrenheit, is expected to affect about 8 million people in the United States this year. But by 2053, 13 times that many people -- 107 million -- will experience that extremely dangerous heat, according to the study.

“The results indicate that the incidence of extreme heat is growing across the country, both in absolute and relative terms,” the study states.

Storm Center 7 Meteorologist Kirstie Zontini said that according to First State Foundation’s model, “across the country, on average, the local hottest 7 days are expected to become the hottest 18 days by 2053.”

The group’s website explains the methodology behind their extreme heat model this way:

“The model estimates localized heat risk at a 30-meter resolution across the United States today and 30 years into the future, creating a high- precision, climate-adjusted heat model that provides insights at a property level. Its analysis combines high-resolution measurements of land surface temperatures, canopy cover, impervious surfaces, land cover, and proximity to water to calculate the current heat exposure, and then adjusts for future forecasted emissions scenarios. This allows for the determination of the number of days any property would be expected to experience dangerous levels of heat.”

As our climate warms, that warm air can hold more moisture. This can lead to hotter and more humid days as the decades go on. Humid air makes it harder for our bodies to cool themselves and increases the threat of heat-related illness. According to the CDC, heat-related illness visits per 100,000 emergency room departments from May-June 2022 has increased in the Upper Midwest, including Ohio, compared to the same months of 2019-2021 combined, Zontini said.

For the full report from the First Street Foundation, click here.

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