High temperatures are in the forecast this weekend for more than 135 million Americans as a “heat dome” looms large over several states. The National Weather Service has warned of record high temperatures over portions of the Midwest, Ohio Valley, and Mid-Atlantic, with heat advisories in effect for many areas.
“The worst of the heat this weekend is going to be in a corridor from Kentucky through Tennessee, in parts of West Virginia and Virginia,” says Bob Larson, Senior Meteorologist at AccuWeather. Areas like Boston and Baltimore are expected to have highs in the upper-90s, while Washington D.C. might see a high of around 100 degrees.
Chicago, Detroit, Pittsburgh, Washington, D.C., Baltimore, and Philadelphia will see above 90 degree temperatures for a week or more, according to AccuWeather, which also predicts that daily high records dating back to the 1920s will be challenged.
Read More: How to Know When the Heat Is Getting Dangerous
For many, relief is on its way. Larson says that regions in the north—including Maine, Vermont, and New Hampshire saw the heat wave peak earlier this week, and that a cold front will bring cooler temperatures as it moves in from the Northwest over the weekend.
The upper Midwest— which includes Minnesota, Wisconsin, and Northern Illinois—are expected to see a cooldown as soon as tomorrow, followed by the Great Lakes region—Michigan, Indiana, and Northern Ohio— on Sunday. While it’ll still be warm, temperatures will be “much more tolerable” across the Northeast by Monday night, Larson says.
But in some parts of the U.S., high temperatures might be here to stay, says Larson, who notes that AccuWeather’s long range forecast is predicting a“hotter than average summer” in the East and Northeast.
And, a “seesaw effect” is expected to occur in the coming days: just as temperatures will begin to cool on the East Coast, the West coast is expected to have a heatwave coming its way.
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Write to Simmone Shah at simmone.shah@time.com