At least nine people have died as a winter storm slammed into the north eastern United States bringing travel chaos as it dumped nearly two feet of snow in some areas.
By Friday morning, about 2,200 flights were cancelled nationwide, according to the aviation tracking website FlightAware.com. Most were in New York, Philadelphia, Boston, Chicago and Washington.
Governors in New York and New Jersey declared states of emergency, urging residents to stay at home. Hundreds of schools were shut in Boston and New York, extending the holiday break for tens of thousands of students.
"This is nothing to be trifled with," New York Governor Andrew Cuomo said. "People should seriously consider staying in their homes."
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 10F (-23C).
Another wave of cold air was already moving through the Midwest after coming down from Canada.
Outreach teams were searching streets in New York City and Boston for homeless people at risk of freezing to death.
Some major roads in New York state were shut down overnight, and some commuter trains around New York City were operating on a reduced schedule.
The heavy weather began rolling in on Thursday, just a day after New York Mayor Bill de Blasio was sworn in to lead the nation's largest city.
Mr De Blasio, who in 2010 criticised predecessor Mayor Michael Bloomberg for his handling of a post-Christmas storm, said 1,700 snowploughs and 450 salt spreaders hit the streets.
"I feel great about the response,"Mr De Blasio said on Friday after shovelling the pavement outside his Brooklyn home. "We are vigilant. We are not out of this yet."
The snowstorm had worked its way east from the Midwest, where it dropped up to 17 ins (431 mls) on parts of Chicago.