Sixteen people have been reported killed by a severe snow storm moving through the north-eastern US after disrupting Christmas in the Midwest.
States in New England are seeing heavy snowfall, with over a foot (30cm) already fallen in parts of Massachusetts, weather officials said.
Flights were grounded and road collisions reported as the storm moved across the middle of the US.
As many as 34 tornadoes were reported across the South on Christmas Day.
The storm moved across northern New England on Thursday afternoon. Heavy snow was also reported in eastern parts of Canada.
Lebanon, Maine reported 12 inches of snow, with up to 18 inches expected in the state and nearby Vermont and New Hampshire through Thursday.
In Coudersport, Pennsylvania, where the storm has stopped, the National Weather Service reported 15 inches.
Hundreds of thousands of people are reported to have lost power, including 200,000 people in Arkansas and Alabama, where ice and 10 inches of snow coated electricity wires snapping poles and wires.
Storm-related deaths were reported in New York, Kentucky, Ohio, Indiana, Arkansas, Oklahoma, Texas, Louisiana, Pennsylvania and Virginia, AP said.
Falling trees claimed the lives of two people in Texas and Louisiana. A New York man was killed after his vehicle skidded on an icy road and an Ohio teenager died after losing control of her car and crashing into an oncoming snowplough.
'Sleet and freezing rain'
As the storm moves into the southern parts of the Canadian province of Quebec, the area could receive up to 17in of snow, according to Environment Canada.
In Concord, New Hampshire, resident Dale Lamprey said he had been on the streets before 05:00 EST (10:00 GMT) on Thursday morning, trying to clear the snow.
"It's been windy, it's been snowing and I think it changed over to sleet and freezing rain at one point. It's pretty bad," he told AP.
Inbound flights were delayed in Philadelphia and at the three New York area airports, as thousands of travellers were trying to return home after Christmas.
In Pittsburgh, a flight that landed safely on Wednesday night got stuck in several inches of snow on the tarmac for about two hours.
Airlines cancelled more than 800 flights on Thursday across the country, according to FlightAware.com.
Flights were also cancelled in Canada, with Toronto and Montreal affected, reports said.
Earlier in the week Little Rock, Arkansas, saw its first snow on Christmas Day in 83 years, while in neighbouring Oklahoma seven inches of snow were blamed for a 21-vehicle pile-up on an interstate highway outside Oklahoma City.
Thirty-four tornadoes were reported in the southern states of Texas, Louisiana, Mississippi and Alabama on Tuesday. A large section of a church roof in Mobile, Alabama, was ripped off by a twister.