A winter storm slammed into the US Northeast with howling winds and frigid cold, dumping nearly 2 feet (60 centimetres) of snow on some areas and whipping up blizzard-like conditions. Thirteen deaths have been blamed on the winter weather.
By midday on Friday (local time), about 2200 flights were cancelled 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.
"This is nothing to be trifled with," New York Governor Andrew Cuomo said. "People should seriously consider staying in their homes."
Officials from the upper Midwest to New England were preparing for another arctic blast over the next few days that could be even worse.
The storm has led to at least 13 deaths as it sweeps across the eastern half of the US 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 (-23 degrees Celsius).
Another wave of cold air already was 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 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 Governor Chris Christie ordered nonessential state workers to stay home on Friday. State offices and courthouses were closed. State offices were also closed in Massachusetts.
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.
De Blasio, who in 2010 criticised predecessor Mayor Michael Bloomberg for his handling of a post-Christmas storm, said 1700 snowplows and 450 salt spreaders hit the streets.
"I feel great about the response," De Blasio said on Friday after shovelling the sidewalk 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 inches (431 millimetres) in parts of Chicago.