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.

A heat wave will intensify along the East Coast this week as tropical humidity levels and 100-degree temperatures reach big cities from Boston to Washington. On Sunday, humidity levels were higher in parts of the Northeast and southern Canada than in Florida,