Iowa is likely to experience more hot days of up to 106 degrees by 2053, climate study shows

The peer-reviewed extreme heat model created by the First Street Foundation, and released Monday, studies the future of climate change in the United States and “identifies the impact of increasing temperatures at a property level, and how the frequency, duration, and intensity of extremely hot days will change over the next 30 years from a changing climate.”

In the study, “Extreme Danger Days” of heat are defined as when the temperature exceeds 125 degrees on a given day. The model predicts 50 counties next year will experience an Extreme Danger Day of heat. But more than 1,000 counties in the United States will experience days of over 125 degrees by 2053.

This emerging area, concentrated in a geographic region the foundation calls the “Extreme Heat Belt,” stretches from the Northern Texas and Louisiana borders to Illinois, Indiana, and into Wisconsin.

“Increasing temperatures are broadly discussed as averages, but the focus should be on the extension of the extreme tail events expected in a given year,” said Matthew Eby, founder and CEO of First Street Foundation. “We need to be prepared for the inevitable, that a quarter of the country will soon fall inside the Extreme Heat Belt with temperatures exceeding 125°F and the results will be dire.”

The top five metropolitan areas with the most neighborhoods expected to experience these Extreme Danger Days are St. Louis, Kansas City, Memphis, Tulsa, and Chicago. 

In Iowa, 63% — or more than 2.4 million homes — have a Moderate Heat Factor due to an increasing heat index — or “feels like” temperatures. The foundation states a property’s heat factor indicates a location’s relative risk to heat, taking into account factors like how heat in the area compares to the rest of the country, as well as how shade, greenspace and proximity to water affect heat at the property. 

The top Iowa counties to likely see the greatest increase in heat waves in 30 years are Fremont, where Sidney is the country seat, in the southwestern corner of the state; Lee, home to Fort Madison, in the southeastern corner of the state; and neighboring Van Buren, home to Keosauqua. 

A heat wave consists of three or more consecutive days where the “feels like” temperature meets or exceeds the local definition of a “hot day,” as defined by the foundation. “Hot day” temperatures in Iowa range from 98 to 106 degrees. 

Though not as severe, 195,342 Polk County properties are also at a Moderate Heat Factor risk.  

Thirty years ago, the likelihood of a three-day or longer heat wave in Polk County was 23%. Today it’s 48%, and the foundation predicts that percentage will rise to 81% in 30 years. 

The “hot day” temperature for Polk County is 103 degrees. The county is expected to experience seven hot days this year. The number of days over 103 degrees doubles in 30 years, according to the foundation’s prediction.