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

The first major heat wave of the summer will bring another day of dangerously high temperatures to the East Coast on Wednesday before relief moves in. The oppressive heat shattered records across the Northeast on Tuesday.

In several cities, including New York, Boston and Philadelphia, temperatures have hovered in the upper 90s, with heat indices exceeding 100°F.