Right now, there are only a few pockets of the U.S. where it’s possible that the heat index might rise above 125 degrees Fahrenheit—a particularly dangerous threshold for human health. But by the middle of the century, climate researchers are predicting that a much larger area is at risk, sprawling from the Gulf Coast across a swath of the middle of the country, and reaching as far north as southern Wisconsin.
The researchers call the area at risk of the worst-case scenario the extreme heat belt. “Currently, there’s only about 50 counties that have any estimate of reaching 125-degree heat index in today’s environment,” says Jeremy Porter, the chief research officer at First Street Foundation, the nonprofit that created the tool and report. “But by 2053, that’s going to grow to about 1,000 counties . . . you go from having about 8 million people today with potential exposure to that level of heat to about 108 million in 30 years.”
But as climate change keeps making heat waves longer and more intense, this summer is also likely to be cooler than most you’ll experience in the rest of your lifetime. The tool shows both the current risks from heat in American cities, and how heat will increase in each location.
The researchers also mapped out “local hot days,” or days above the local 98th percentile temperature. Someone living in a place where it’s usually cooler, such as Seattle, might start to see health impacts at a lower temperature than someone living in Phoenix who is more acclimated to heat (that person living in a historically cooler region is also less likely to have air-conditioning). Someone who’s planning to relocate might use the tool to reconsider.