Parts of the US and Canada are braced for potentially record-breaking low temperatures as a blast of arctic air blows across North America.
A winter storm has already blanketed areas of Canada and the north-eastern US with up to 2ft (60 cm) of snow.
More than 3,000 flights were cancelled on Monday, on top of thousands grounded over the weekend.
Schools have been closed in several US states and residents urged to stay indoors for their own safety.
The storm and the deep cold have been blamed for 16 deaths in recent days.In developments across the region:
A power failure in Newfoundland, in Canada, late on Sunday left 90,000 homes without electricity. It was a blow to residents already trying to deal with rolling blackouts and the aftermath of a blizzard, CTV News reports
The National Weather Service in Kansas City predicted a low of -22C (-8F) for Monday morning, shy of the record low for this date of -25C (-13F) set in 1912. But life-threatening wind chills will make it feel much colder, the Kansas City Star reports
South Dakota's Keloland.com carries a report about farmers trying to keep their cattle warm, as the cold weather can have a devastating impact on herds
In Indiana, a state of emergency has been declared in several north-west counties, allowing only emergency or law enforcement vehicles on the roads
In Thunder Bay, Ontario, where the temperature on Monday morning was -33C (-27F), skate rental business owner Roy Laham told the Chronicle-Journal newspaper he had only 20 customers on Sunday, down from the usual 200-300Temperatures in the north and central US could feel as low as -51C (-60F) with the effect of wind chill, forecasters say.
"The coldest weather in years will be making its presence known from the Upper Midwest to the Mid-Atlantic region for the beginning of the work week," the US National Weather Service said in a statement.
The states of Ohio, South Dakota and Illinois are among those set to be hit. Tennessee and Kentucky are forecast to see several inches of snow.
It is set to continue to the north-east, where residents are still digging out from the week's deadly snowstorm.
In eastern Canada, the temperatures are expected to drop quickly throughout Monday. Freezing rain caused long airport delays in Toronto and Ottawa.
