WASHINGTON: The northeastern United States hunkered down Tuesday for a major snowstorm that forecasters warned could leave as much as one foot (30 centimetres) of snow in some places.

Downtown Washington fell virtually silent after the federal government, seeing the swift-moving cold front approaching, closed its doors and told civil servants to stay home.

Many offices and schools followed suit, as 20 mile (32 kilometre) per hour winds whipped the falling snow through the unusually quiet streets.

Enough snow was expected to fall on the US capital to turn the evening rush hour into a Beltway traffic nightmare, as the storm churned its way into New York and the northeastern New England states.

"The greatest totals are likely for southern New England, and gusty winds are likely in this area to accompany the snow," the National Weather Service said.

"It will be a winter wonderland for these areas."

FlightAware, a website that monitors air traffic, said more than 2,800 flights into, out of or within the United States had been cancelled -- with the greatest number involving airports in the New York, Philadelphia and Washington areas.

National passenger rail operator Amtrak said its trains were operating on "a normal Tuesday schedule," but it warned passengers to "anticipate some weather-related delays."

Private forecasting service AccuWeather expected snowfalls to be heaviest along a band stretching from the Canadian province of Nova Scotia and the northeastern-most state of Maine down the Atlantic seaboard into Virginia.

"Travel conditions will deteriorate rapidly due to slippery roads and diminishing visibility," AccuWeather said.

"As the air turns colder, the snow will become dry and powdery. Increasing winds will cause extensive blowing and drifting snow."

The Washington Post's popular Capital Weather Gang blog forecast up to 10 inches of snow in the US capital, ahead of a return of sub-freezing temperatures later this week.

Smithsonian museums along the National Mall opened as usual Tuesday, and planned to stay open as long as conditions allowed.

But the National Zoo shut its gates -- giving its star attraction, baby panda Bao Bao, the day off just three days after going on public view for the first time.

Organizers of Wednesday's annual March for Life rally on the National Mall, which typically draws tens of thousands of opponents of abortion, said they were going ahead with the event.

In New York, a storm alert was issued for noon (1700 GMT) Tuesday to 6:00 am (1100 GMT) Wednesday with as much as a foot (30 centimetres) forecast for the metropolitan region.

Temperatures were set to fall below normal, to as low as 10 degrees Fahrenheit (minus 12 Celsius) with winds gusting to 35 miles (56 kilometres) per hour.

Dozens of schools either closed for the day or told parents to expect their youngsters to be dismissed from class earlier than usual.

New Jersey went ahead with its mid-day inauguration ceremony for re-elected governor Chris Christie, but an evening celebration on Ellis Island in New York harbour was cancelled due to the storm.

What the National Weather Service called a "fast moving but potent" snowstorm had earlier dumped seven inches of snow at airports in the Chicago area, before temperatures fell to the freezing level, local media reported.