NYC will jump from a clear start to near-90-degree heat Wednesday, followed by late-night storms and possible coastal flooding near high tide.

The warning put 3.4 million people and 804 schools in its path as a fast-moving storm system swept through.

Las Vegas will hit about 102°F Tuesday before afternoon thunderstorms bring lightning, brief rain and gusty winds. A short midweek cooldown arrives before another heat rebound.