© AP PhotoSnow was being cleared from the M&T Bank Stadium in Baltimore ahead of an NFL game on Sunday
Storm-related incidents claimed five lives and forecasters warned of 40mph (64km/h) winds in what may be the worst snowstorm in a decade.
Snowfall is due to reach 22in overnight in the Baltimore-Washington DC area, the heaviest since 2003.
The storm system is moving north toward New York and Boston.
Forecasters say the cities could be in for more than 14in of snow.
In Washington, a snow emergency was declared and the capital's Reagan National Airport has been shut down for the night.
Most flights from Baltimore were canceled and there were long delays for passengers using Philadelphia and New York.
Roads have been badly affected, too, with one transport official calling it a very serious storm.
As Washington's Union Station filled with travelers, some of them sprawled out on the floor, the passenger train service Amtrak said delays between Washington and Boston were averaging between 30 and 60 minutes.
At least two trains to Boston apparently departed more than four hours late.
© AP PhotoWashington DC is preparing for its worst winter since 2003
In Virginia, several hundred motorists became stranded in their vehicles and had to be rescued by the National Guard, using Humvees.
Some 500 people sought warmth and refuge in emergency shelters.
Three people died in the state. One was killed when a car hit a tree, a second died of exposure and a third was also apparently killed in a road traffic accident.
In Ohio, two people were killed in accidents on snow-covered roads hit by the same storm system.
The US National Weather Service said the storm was expected to reach as far north as Massachusetts on Sunday.
Heavy snow is expected to fall from North Carolina to New York, with major cities bracing themselves for a foot or more of snow.
The US National Weather Service warned that weather conditions in the Washington area had made travel "extremely treacherous".
"Do not travel," it warned drivers.
"If you must travel, have a winter survival kit with you. If you get stranded, stay with your vehicle."
Empty malls
Washington Mayor Adrian Fenty asked residents to sit out the weekend snowstorm at home where possible.
Those who did venture out were treated to nearly desolate stores on what is usually one of the busiest shopping days of the year, The Associated Press reports.
In snow-bound areas, there were virtually no queues to get a picture with a mall Santa on the last weekend before Christmas, it adds.
"It's nice because no one's here," said shopper Nnika White, out buying a drum set for her boy of two in Richmond, Virginia.
"For shopping, it's great, but the roads are very, very bad," she added.
US President Barack Obama, arriving back at Andrews Air Force Base in Virginia from the Copenhagen climate conference, travelled into Washington by motorcade rather than helicopter because of the weather.
The storm system originated over the Gulf of Mexico, unleashing flash floods in much of the US south-east.
The rain turned to snow as the storm tracked north-eastward into sub-freezing temperatures.
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