Much of the U.S. is under extreme heat warnings or advisories while New York, Philadelphia and Washington could feel like 100 degrees or more.

A phenomenon called "corn sweat" could exacerbate the impacts of the extreme heat blanketing a large portion of the U.S., according to experts.

An intense heat wave threatens millions of people across the Southeast with temperatures reaching 115 degrees through midweek.

Aside from an isolated shower or storm mainly South of I-88, most in the Stateline should stay dry this evening. Temperatures will gradually fall to the low 70s, meeting the dew point under a calm wind.

The National Weather Service released an updated extreme heat warning at 12:53 p.m. on Friday in effect until 9 p.m. for Eastern Montgomery and Lower Bucks as well as Delaware and Philadelphia counties.

A heat advisory will continue Sunday afternoon before late-day thunderstorms cool things down. More heat and storms are likely through the workweek.

Heat advisories were in effect for a large portion of the East Coast from central Florida to Virginia through much of the weekend.