A significant heat wave is currently impacting at least 40 million people across the central and southern United States, marking the second consecutive day of extreme temperatures and severe humidity. Heat indexes are projected to climb well above 100 degrees Fahrenheit (38 Celsius) from Minnesota southward to Mississippi, and westward into southern California and Nevada.
Parts of the Southwest are bracing for highs reaching 120 degrees Fahrenheit (49 C), according to the National Weather Service. Meteorologists attribute the intense heat to a heat dome, an atmospheric condition that traps heat and intensifies existing high temperatures.
"It's extraordinarily hot," said Pete Miller, an outreach manager for the homeless services network Threshold CoC, which distributed water bottles to residents in Omaha, Nebraska. "We're seeing a lot of people who are exhausted, drained by the heat in a way that is really dangerous. The humidity is insane. You stand outside for 30 seconds and you get drenched. And it's going to be like that all night."
On Saturday, Rapid City, South Dakota, recorded an all-time high of 112 degrees Fahrenheit (44 C). A horse race scheduled for Sunday at Canterbury Park in Shakopee, Minnesota, was canceled due to the heat.
"Right now, it's affecting a lot of people right in the middle of the country," said Bob Oravec, an NWS meteorologist. "The core of the heat sinks southward by early next week."
The high humidity also contributes to volatile weather patterns around the periphery of the heat dome. The Great Lakes region faces risks of severe thunderstorms, flash flooding, and hail on Sunday, with the potential for heavy storms expected to shift eastward in the coming days.
"If you have a heat dome in one part of the country, you'll have a different corresponding weather in another part," Oravec explained. "It's all related."
Forecasters anticipate some temporary relief in the central U.S. by the middle of the week, though high temperatures could return by the weekend. Authorities are emphasizing the risks to children, older adults, and individuals with pre-existing medical conditions, warning of potential heat stroke and even death. Recommendations include seeking air-conditioned spaces or cooling centers, staying hydrated, and limiting direct sun exposure.
Extreme heat events are known to be exacerbated by climate change, which is driven by the combustion of fossil fuels. The continental U.S. experienced the second-hottest first half of the year on record in 2023, according to data from the National Centers for Environmental Information.