Major Heat Wave to Blanket Central and Eastern U.S. Through the Week

A major heat wave is set to sweep across the central and eastern United States beginning Tuesday, bringing dangerously high temperatures and raising serious health concerns for tens of millions of people.

The heat builds first across the Plains, where highs in the upper 90s to low 100s are expected Tuesday, with lower 90s reaching parts of the Midwest and Mississippi Valley. The heat index, which reflects how hot it actually feels when humidity is factored in, will push even higher than the raw temperature numbers suggest.

By Wednesday, the Weather Prediction Center says nearly 50 million people will be under a level three out of four "major" heat risk. That number jumps to more than 80 million by Thursday, when the worst of the heat reaches the East Coast. New York City is forecast to hit around 93 degrees, which would match its highest temperature recorded so far this year.

The heat will also fuel severe thunderstorms across the central U.S. on Tuesday, adding another hazard alongside the temperature extremes.

Conditions are expected to begin easing over the weekend in the East, with much cooler air arriving early next week and widespread highs dropping into the 70s and 80s.