Almost the entire East Coast and Southeast — 84 million people in all — are at risk for severe weather on Tuesday.
The risk zone outlined by the National Weather Service stretched from the Louisiana-Texas state line east to Atlanta and up the coast to Boston.
It was already raining Tuesday morning in Washington, Philadelphia and New York, making for a messy commute. Flights coming into LaGuardia and John F. Kennedy International Airports were delayed by more than an hour.
Some of the storms could produce damaging wind and flash floods. The Weather Channel reported that a tornado could not be ruled out in New England. Strong storms could also flare up in the central and southern Rockies and parts of the Southwest.
On Wednesday, the severe-weather threat should be confined to the Southeast, the Rockies and the Southwest, according to the Weather Channel.