Tens of millions of people across the Midwest and East are enduring another sweltering day of dangerously hot temperatures as a sprawling June heat wave grips much of the U.S.

A multiday heat wave is bringing high temperatures and health risks from the Midwest to the Northeast, prompting warnings and emergency measures.

The temperature made it to 91 on Saturday in Philly, and by the end of the workweek, that kind of heat may seem like a cool shower. By then, said Zack Taylor, chief of the analysis section at the National Oceanic and Atmospheric Administration’s Weather Prediction Center,