At least 40 million people faced extreme heat warnings across central and southern parts of the United States on Sunday as high temperatures and severe humidity gripped large swaths of the country for a second straight day. Heat indexes well above 100 degrees Fahrenheit stretched from Minnesota to Mississippi and extended west into southern California and Nevada, driven by a persistent heat dome trapping hot air across the region.
Extreme Heat Grips the Central and Southern US
The dangerous conditions placed roughly 40 million residents under extreme heat warnings on Sunday. Heat indexes climbed well past 100 degrees Fahrenheit (38 Celsius) throughout the central and southern regions, stretching from Minnesota down to Mississippi while reaching westward into southern California and Nevada, according to the National Weather Service. Meteorologists reported that parts of the Southwest could see highs reach 120 degrees Fahrenheit (49 C).
The sweltering weather is the result of a heat dome, an atmospheric phenomenon that traps heat and amplifies already high temperatures over a prolonged period. On Saturday, Rapid City, South Dakota, reported an all-time high of 112 degrees Fahrenheit (44 C). The intense heat disrupted local events, forcing the cancellation of a horse race planned at Canterbury Park in Shakopee, Minnesota, on Sunday.
On-the-ground impacts were immediate in vulnerable communities. In Omaha, Nebraska, Pete Miller, an outreach manager for the homeless services network Threshold CoC, spent Sunday handing out water bottles to residents. “It’s extraordinarily hot,” Miller said, describing conditions where people were exhausted and drained in a dangerous way. “The humidity is insane. You stand outside for 30 seconds and you get drenched. And it’s going to be like that all night.”
Widespread Weather Volatility and Storm Risks
The atmospheric pressure creating the heat dome also generated severe weather volatility in surrounding regions. On Sunday, moist air circulating near the top of the heat dome produced risks of severe thunderstorms, flash flooding, and hail around the Great Lakes, according to National Weather Service meteorologist Bob Oravec. The potential for these heavy storms is expected to move east 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 said, emphasizing that the weather systems are connected. Oravec noted that the core of the heat is expected to shift southward by early next week, bringing temporary relief to the central U.S. toward the middle of the week. However, high temperatures could return by the weekend.
The event coincides with broader climate trends tracked by federal agencies. Extreme heat events are increased and exacerbated by climate change resulting from the burning of fuels like gasoline, oil, and coal. According to tracking of average temperatures by the National Centers for Environmental Information, the continental U.S. endured the second-hottest first half of the year on record in 2026.
Health Risks and Safety Guidance
Authorities issued warnings that children, older adults, and people with certain medical conditions face an elevated risk of serious health conditions, including heat stroke or even death, due to the persistent high temperatures and severe humidity.
To mitigate these dangers, experts recommend seeking out air conditioning or a designated cooling center, ensuring adequate water intake, and limiting time spent directly under the sun.