(CNN) -- Crews worked to restore power Monday to more than 400,000 homes as a powerful low-pressure system churned off the Eastern Seaboard.
"High winds are over, but the rain and flood threat remain in the mid-Atlantic and Northeast," CNN meteorologist Jacqui Jeras said. "There are major travel delays -- and more expected on Monday."
Some coastal areas have received more than 6 inches of rain since Saturday, according to the National Weather Service. Flood warnings remained in effect from Maryland to Maine.
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Flooding in West Virginia caused one death there, authorities said. Two men died Sunday in Teaneck, New Jersey, after a tree fell on their vehicle.
Con Edison said more than 100,000 customers were without power in New York City and Westchester County on Sunday, while the Long Island Power Authority said that 95,000 customers were without electricity. In New Jersey, about 185,000 were without power. In Connecticut, the number was 65,000.
"The ground is so wet from all the snow we've had this winter, it's helping the trees to topple over as well as our utility poles," said Long Island Power Authority President and CEO Kevin Law. "The conditions are still too terrible to get crews out there."
Some customers probably will go without power for several days, Law said.
Wind speeds reached 75 mph Saturday at New York's John F. Kennedy International Airport -- as strong as a Category 1 hurricane -- and 72 mph in Atlantic City, New Jersey.
New York-area airports reported delays of at least two hours Sunday, while Boston's Logan International Airport averaged 40-minute delays.
No significant delays were reported Monday morning.
In the Midwest, flooding continued Sunday because of snow melt, rain and ice jams.
Farther west, the Red River is expected to reach major flood stage around Fargo, North Dakota, and adjacent Moorhead, Minnesota, on Tuesday.