About 70 million Americans are under some level of heat advisory or warning, the National Weather Service said, with portions of the Midwest and Northeast forecast to see the heat index nearing 100 degrees this week.
Some high temperature records could be broken, the weather service said.
“With the school year getting started in many areas, it could be a very uncomfortable few days for students and teachers in schools without air conditioning,” AccuWeather meteorologist Brian Thompson said.
In the Northeast, heat advisories are posted for a swath of the mid-Atlantic states, New York and New England, including the entire New York City Tri-state area and Philadelphia metros, the Weather Channel said. Excessive heat watches for more dangerous heat indices are posted for the Boston and Hartford metro areas.
In New York City, players and spectators alike will endure stiflingly hot and humid weather at the 2018 U.S. Open, according to AccuWeather.
In St. Louis, the entire metro area is under an excessive heat warning, the highest level of heat advisory issued by the weather service. The heat can be “a dangerous situation in which heat-related illnesses are likely, especially for those living in un-air conditioned homes or apartments,” the weather service said.
A few severe thunderstorms could also rattle across the northern Plains later Monday and into Tuesday.
The heat is due to a ridge of high pressure building in the nation’s midsection, one that will shift toward the East Coast early this week, the Weather Channel said.
Air sinks under areas of high pressure, which prevents clouds and storms from forming. That area of high pressure is responsible for the return of sultry temperatures.
A brief cool-down is forecast for later this week, the Weather Channel predicts, before another possible heat wave next week.
If you’re looking for cool weather this week, head for western portions of Wyoming and Montana, where up to 8 inches of snow is possible today and Tuesday.