A life-threatening heat wave has enveloped the East Coast, hitting cities with the worst of the high temperatures on Tuesday before relief moves in later in the week.This is the first major heat wave of the season,

A long-lasting extreme heat wave is reaching its dangerous crescendo Tuesday, likely bringing the hottest day in a decade to some major East Coast cities and putting millions of already fatigued Americans at risk.

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,