Late-season snowstorm weakens in the U.S. Northeast

Schools have been closed, flights grounded and electricity knocked out to hundreds of thousands as a late-season snowstorm hit the USA.

Despite the storm starting to weaken on Wednesday, millions of people on the East Coast continue to face temperatures 10 to 25 degrees below average, wind gusts of 50km/h and slick roads and sidewalks, the National Weather Service said.

"Residual snow and slush will refreeze early this morning, resulting in hazardous conditions on roads and walkways," it said, urging extra caution by those venturing out early.

Skiers took to Central Park on Tuesday. Picture: AAP

A man works to clear snow in Washington DC. Picture: AAP

The rare mid-March storm was tapering off over upstate New York and northern New England after dumping as much as 30cmof snow on Tuesday, the weather service said.

As life returns to normal for many, students in Boston Public Schools had the day off while the city and surrounding area continues to dig out from heavy snowfall.

Amtrak said its trains would operate on a modified schedule between New York City and Boston and between New York City and Albany on Wednesday.

As the snow eased, New Yorkers were able to get out and about in Central Park. Picture: AAP

On Tuesday, snow fell from the lower Great Lakes and central Appalachians to the Eastern Seaboard and as far south as North Carolina.

Some cities, such as Washington, D.C., and New York, got just a few inches of snow, far less than the anticipated amounts that forced public officials to close schools, shut down commuter train routes and warn people to stay indoors on Tuesday.

Governors in New York, New Jersey, Pennsylvania and Virginia declared states of emergency at the outset of the storm.

Thousands of passengers were stranded at airports around the country. Picture: AAP

"Mother Nature is an unpredictable lady sometimes," New York Governor Andrew Cuomo told a news conference on Tuesday.

"She was unpredictable today."

More than 6,000 commercial airline flights across the United States were cancelled for on Tuesday with airlines working to clear the backlog on Wednesday.