Government offices and schools closed several hours ahead of schedule in Washington on Friday to enable people to head home before a major snowstorm hit.
The snowfall in the national capital was already lowering visibility by late afternoon and threatening to bring all public services to a standstill.
A "monster" blizzard was blowing across the mid-west and towards the mid-Atlantic coastal region, where it is expected dump 30 to 60 centimetres of snow over 24 hours from Friday to Saturday.
The huge storm system has been heading up from the south all week, where it dropped rain and lesser amounts of snow.
Winter storm warnings were in place from southern Indiana eastwards to New York City and south to North Carolina, with blizzard warnings for Delaware and the New Jersey coast, according to the National Weather Service.
Delta Airlines canceled all flights to and from the Washington, Baltimore and Philadelphia on Saturday, but hoped to revert to normal schedules by Sunday.
Amtrak canceled most of its train services from Washington headed south.
The Metro system in Washington plans to close above-ground stations when the snow reaches 20 cm.
Washington Mayor Adrian Fenty declared a snow emergency that went into effect at Friday morning, which prevents people from parking on certain streets so snow plows can get through.
Strong winds and plunging temperatures are expected to make for extremely hazardous travel, the National Weather Service said.
Weather forecaster AccuWeather advised people to plan on "no travel" from Friday night into Saturday night in Virginia, Maryland, Delaware, southern Pennsylvania and much of New Jersey.