Heat index values climbed well above 100 degrees Fahrenheit (38 degrees Celsius) from Minnesota to Mississippi, while the National Weather Service forecast temperatures as high as 120 F (49 C) in parts of the Southwest, including southern California and Nevada.

Meteorologists said the prolonged heat is being caused by a heat dome, an atmospheric weather pattern that traps warm air over a region, allowing temperatures to remain exceptionally high for several days.

Extreme Heat Strains Communities

Communities across the affected region reported growing concerns about the impact of the prolonged heat, particularly on vulnerable populations.

Pete Miller, outreach manager for the homeless services network Threshold CoC in Omaha, Nebraska, said volunteers were distributing bottled water to people exposed to the dangerous conditions.

“We’re seeing a lot of people who are exhausted, drained by the heat in a way that is really dangerous,” Miller said. “The humidity is insane. You stand outside for 30 seconds and you get drenched. And it’s going to be like that all night.”

The extreme temperatures also disrupted public events.

Canterbury Park in Shakopee, Minnesota, canceled scheduled horse racing on Sunday because of the weather, while Rapid City, South Dakota, recorded an all-time high temperature of 112 F (44 C) on Saturday, underscoring the severity of the heat wave.

Forecasters Warn of Severe Storms

National Weather Service meteorologist Bob Oravec said the center of the heat dome is expected to shift farther south early this week.

“Right now, it’s affecting a lot of people right in the middle of the country,” Oravec said. “The core of the heat sinks southward by early next week.”

Forecasters said the same weather pattern producing the extreme heat is also creating instability along the edges of the heat dome.

Areas around the Great Lakes face the risk of severe thunderstorms, flash flooding and large hail, with the threat expected to shift east during 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. “It’s all related.”

He added that parts of the central United States could experience temporary relief by the middle of the week, although high temperatures may return next weekend.

Officials Urge Heat Safety Precautions

Public health officials urged residents to take precautions as prolonged exposure to extreme heat increases the risk of heat exhaustion and heat stroke, particularly among children, older adults and people with underlying medical conditions.

Authorities recommended staying in air-conditioned buildings or designated cooling centers whenever possible, drinking plenty of water and limiting outdoor activities during the hottest hours of the day.

According to the National Centers for Environmental Information, the continental United States recorded its second-hottest first half of the year on record in 2026 based on average temperatures.

Scientists say climate change driven largely by greenhouse gas emissions has increased the frequency and intensity of extreme heat events, although the influence on individual weather events is assessed through longer-term scientific analysis.

This report is based on reporting by The Associated Press.