US authorities have warned people to stay at home as parts of the north-east and Midwest are battered by snowstorms and blizzard-like conditions.
The authorities have asked people to dress warmly
"If you leave the safety of being indoors, you may be putting your life at risk," the National Weather Service said. Snowfall records may be set.
In Boston, about two inches an hour (5cm) was falling with winds of up to 42mph (68km/h).
More than 1,000 flights have been cancelled because of the weather.
The worst-hit airport was Chicago's O'Hare, with some 700 cancellations. Airports in New York, Boston and Philadelphia are also affected.
Drivers have been warned of blizzards across large areas of the US - from Wisconsin to Virginia and New England.
A series of power cuts have been reported and conditions are expected to get even worse, meteorologists warn.
They say the collision of a cold front moving in from the Great Lakes region and warmer air from the Atlantic will produce ferocious blizzards and winds of up to 50mph (80km/h).
Forecasters said they expected a record snowfall in Boston, Massachusetts.
"The jackpot will be eastern Massachusetts where 28 to 38 inch amounts (71-96cm) are likely," National Weather Service forecasters said.
"This is likely to be a record-setting snowstorm in Boston when comparing against data dating back to 1892."
Flight delays are forecast for some time to come
"The snow is falling not in inches but in feet," said Governor Mitt Romney. He warned of possible tidal surges in coastal areas as a result of the full moon.
In New York City (NYC), at least 30cm (a foot) of snow was expected.
"This really is a dangerous storm," New York Mayor Michael Bloomberg said at a news conference on Saturday.
"I don't think you should take it lightly."
Mr Bloomberg urged residents to dress warmly, check on neighbours and keep their cars off the roads to allow the removal of the snow.
New Yorkers were stocking up on supplies to ride out the storm indoors.
In Mamaroneck, north of New York City, long queues had formed at a local store where people stripped the shelves of meat, potatoes, and beer.
"It's awesome," store manager Louis Spinola said.