A blast of rain and snow along the East Coast snarled traffic and disrupted flights for millions of Americans at the start of the long Thanksgiving weekend, traditionally the busiest time of the year for U.S. travel.

The nor'easter that formed over the Gulf of Mexico brought rain to cities including New York and Boston. Higher elevations in New England will see about a foot of snow, National Weather Service meteorologist Andrew Orrison said on Wednesday.

"Either way, travel is not going to be in a good state," Orrison said.

Parts of Virginia, West Virginia, Pennsylvania and Maryland saw more than 6 inches of snow on Wednesday, according to the weather service.

More than 700 flights into and around the United States were canceled on Wednesday and about 4,400 were delayed, according to tracking website FlightAware.com.

"I just hope I can get on the plane," Amber Fernandez, 19, said at New York's LaGuardia Airport, where she waited to board a flight to Detroit that had been delayed about two hours.

The Thanksgiving holiday is one of the busiest travel times in the United States, with more than 46 million Americans expected to make trips between Wednesday and Sunday, travel group AAA said. More than 89 percent will travel by car, it said.

In New York, where a snowstorm last week killed at least 13 people, Governor Andrew Cuomo urged travelers to drive with caution.

The state has reserved snowplows to respond to emergencies and has more than 130,000 tons of road salt to use between New York City and Albany.

The Port Authority of New York and New Jersey said it would increase staffing at its airports and toll collection booths at its tunnels and bridges to accommodate an increase in holiday travelers.

Across Pennsylvania, stormy weather caused accidents that brought traffic to a halt on several major roadways, the state's Department of Transportation said.

"As it gets colder tonight, a frozen crust will form and we'll have to treat and plow them," said snowplow operator Henry Hobbs, 44, in northern Maryland.

A region spanning from Florida to Maine will be hit by rain from the storm, while heavy snowfall is anticipated from the central Appalachians to the inland Northeast, the weather service said.