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.

More than 160 million Americans are under the highest level of extreme heat alerts during a wave of above-average temperatures.