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.
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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.