Residents began digging out of the snow and ice Saturday after a winter storm slammed the US Northeast with howling winds and frigid cold, dumping nearly 2 feet (60 centimeters) of snow on some areas.
The storm left at least 16 people dead amid blizzard-like conditions, authorities said.
As motorists and homeowners emerged from the white-blanketed region, officials from the upper Midwest to New England were preparing for another arctic blast over the next few days that could be even worse.
By midday Friday, about 2,200 flights were canceled nationwide, according to the aviation tracking website FlightAware.com. Most were in New York, Philadelphia, Boston, Chicago and Washington, DC.
Governors in New York and New Jersey declared states of emergency, urging residents to stay at home. Hundreds of schools were shut down in Boston and New York, extending the holiday break for tens of thousands of students.
The heaviest snow fell north of Boston in Boxford, Massachusetts, which received nearly 2 feet (0.61 meters). Nearly 18 inches (46 centimeters) fell in Boston and in western New York near Rochester. New York's Central Park and Philadelphia each got 6 inches (15 centimeters).
The storm has led to at least 16 deaths as it sweeps across the eastern half of the U.S. Slick roads have caused traffic deaths in Michigan, Kentucky, Indiana and Illinois.
A massive pile of salt fell on a worker at a Philadelphia storage facility, killing him. And authorities say a woman with Alzheimer's disease froze to death after she wandered away from her rural New York home.
Forecasters said temperatures were plummeting to well below freezing, and wind chill readings could hit minus 10 Fahrenheit (minus 23 Celsius).
Another wave of cold air already was moving through the Midwest after coming down from Canada. Temperatures in the midwest and the northeast are expected to rise briefly over the weekend before the arrival of another blast of extraordinarily cold air.
Minnesota Gov. Mark Dayton ordered school canceled on Monday statewide, the first such closing in 17 years, because of projected highs in the minus teens and lows as cold as 30 below.
The cold air could refreeze roads that are wet or slushy from the weekend thaw, making travel dangerous.
Outreach teams were searching streets in New York City and Boston for homeless people at risk of freezing to death.
Some major highways in New York state were shut down overnight, and some commuter trains around New York City were operating on a reduced schedule.
New Jersey Gov. Chris Christie ordered nonessential state workers to stay home Friday. State offices and courthouses were closed. State offices were also closed in Massachusetts.
The heavy weather began rolling in Thursday, just a day after New York mayor Bill de Blasio was sworn in to lead the nation's largest city.
De Blasio, who in 2010 criticised predecessor mayor Michael Bloomberg for his handling of a post-Christmas storm, said 1,700 snowplows and 450 salt spreaders hit the streets.