Topline
More than 60 million people across the South and Midwest are already feeling the effects of a "heat dome" that could last weeks and bring triple digit temperatures to major cities that haven't seen them yet this year.
Farm workers weed a bell pepper field in the sun.
The National Weather Service has issued heat advisories across parts of 19 states with more intense extreme heat watches in Wisconsin, Iowa and Illinois.
Even more dangerous extreme heat warnings are in effect in parts of Illinois, Missouri, Arkansas, Tennessee, Louisiana and Mississippi.
Major cities under heat alerts include Dallas; New Orleans; Memphis, Tennessee; Little Rock, Arkansas; St. Louis; Kansas City, Missouri; Chicago and Minneapolis.
In Dallas, temperatures could reach 100 degrees on Thursday and Friday for the first time this year and Kansas City, which hasn’t seen 100-degree weather in two years, could also hit triple digits.
Heat indexes, also called the "feels like" temperature, will be in the 100- to 110-degree range across the central Plains and Southeast for the rest of the week, and the heat is forecasted to extend to the East Coast on Friday.
The high temperatures are thanks to what meteorologists call a "heat dome"—a high-pressure build up of hot, humid air caused by a bulge in the jet stream—which is expected to "linger through a good chunk of August," Accuweather's Alex Sosnowski predicts.
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More heat. The Climate Prediction Center's latest forecast shows August will be another hot month for most of the country, with a high chance for above-average temperatures almost everywhere.
The midwest, much of which is currently under the heat dome, is also particularly susceptible to a phenomena called evapotranspiration, or "corn sweat." The phrase describes a process by which plants, including corn, release water vapor into the air and increase humidity, contributing to the feel of oppressive heat. States with large swaths of farm land—like the 30 million acres in Iowa and 27 million acres in Missouri—are particularly vulnerable. Iowa state climatologist Justin Glisan described corn sweat to the Washington Post as feeling “like being fully clothed in a sauna or steam room.”
The last several summers have been reported as the hottest summers on record. Globally, 2024 was once again the hottest year on record and temperatures last year were 2.3 degrees Fahrenheit above NASA’s 20th-century baseline. The record was broken after 15 consecutive months of monthly record-setting temperatures (from June 2023 through August 2024). July 22, 2024 was the hottest day ever recorded—global surface air temperatures reached an average of 62.87 degrees Fahrenheit. The most recent month to break global temperature records was January. So far, 2025 isn’t expected to top 2024.
Extreme cold is much more likely to kill than exposure to extreme heat. Hypothermia, frostbite and worsening of pre-existing medical conditions are often deadlier than problems brought on by hot weather, though heat-related deaths have been on the rise in the U.S. More than 2,300 people died of causes tied to heat in 2023, and heat-related deaths have spiked 117% since 1999.
The National Weather Service has warned people in extreme heat to stay safe by staying hydrated, wearing sunscreen, wearing loose-fitting and light-colored clothing and limiting time outdoors. Increasing heat waves pose particular dangers to the outdoor workers who often labor under the sun for hours per day—many with no workplace protections. Workers in more than 40 states have no regulations governing shade, rest or water on the job, and there are no heat-specific regulations mandated by the Occupational Safety and Health Administration beyond recommendations for employers when temperatures reach above 91 degrees. Only five states have heat exposure standards for all outdoor workers—California, Minnesota, Colorado, Oregon and Washington, according to OSHA. Joe Biden brought forth a new rule intended to protect workers last year, and the comment period on the proposed regulations ends in September.