Extreme Heat Dome Puts Eastern U.S. Under Widespread Risk

Tens of millions of people across the eastern U.S. are set to experience dangerous heat conditions over the coming week due to a persistent heat dome, meteorologists report. High humidity and warm nights are expected to push heat alerts across the region, making the heat wave harder to escape.

Risk Expands Daily

On July 23, more than 35 million people were already under “major or extreme” heat risk, mainly across the Mississippi River Valley, according to the National Weather Service (NWS). This number is expected to double on July 24 as the heat spreads east, affecting nearly 90 million people by July 25.

“Even though it’s midsummer, this is pretty notable,” said Bryan Jackson, a meteorologist at the NWS Weather Prediction Center in Maryland.

What Is a Heat Dome?

A heat dome forms when a high-pressure system traps warm air beneath it. The jet stream, a fast-flowing air current in the upper atmosphere, often contributes to this setup. Such patterns are known to last for days or even weeks, worsening day by day.

“Heat domes are generally slow to form and slow to dissipate,” Jackson added.

Little Relief Even at Night

Humidity is playing a major role in making this heat wave more oppressive. Nighttime temperatures are staying unusually warm, offering minimal relief.

“With the high moisture we are seeing, there will actually be quite a few record-high minimum temperatures,” Jackson explained.

Affected Areas & Timeline

Currently centered over Memphis, Tennessee, the heat is moving across various regions. The Ohio River Valley will see peak conditions on July 24, followed by the Eastern Seaboard on July 25. The Southeast, Carolinas, and Mid-Atlantic are expected to face record-setting overnight temperatures over the weekend.

Climate Change’s Fingerprint

Prolonged heat events are becoming more common. Recent data reveals that many eastern U.S. cities are now experiencing more frequent “heat streaks”—three or more consecutive days with extreme daily high temperatures compared to past decades.

For those in the affected areas, experts advise checking science-based guidance on how to stay safe in extreme heat and keeping your homes cooler.