An Arctic snap gripped most of Canada and a large swath of the northern United States on Wednesday, with unusually low temperatures recorded in both countries.
In Canada, extreme cold warnings were issued for scores of communities across the country, including the heavily populated provinces of Ontario and Quebec.
While Toronto reported temperatures of minus 15 C (5 F) and Ottawa minus 25 C, the coldest spot in Canada was minus 42.8 C in Armstrong, Ontario, according to Environment Canada.
Extreme cold warnings are issued "when very cold temperatures or wind chill creates an elevated risk to health such as frost bite and hypothermia," the government agency said.
The temperatures were 10 to 20 degrees below what is normal for the season, said meteorologist Alexandre Parent with Environment Canada.
The deep cold is forecast to remain until early January, he said.
"In my memory I have never seen cold weather that settles for such a long time in such a broad expanse," Parent said.
High winds of up to 120 kilometers (76 miles) per hour linked to the low temperatures have left almost 160,000 homes in the eastern province of Nova Scotia -- almost one-third of the power company's customers -- without electricity, officials said.
- Record snowfall in Eire -
In the United States, brutal sub-zero temperatures were recorded in places like Duluth, Minnesota (minus 37.7 C) on Tuesday, and Minot, North Dakota (minus 29 C).
A storm dumped a record-breaking five feet (nearly 1.5 meters) of snow in a 48-hour period on the Pennsylvania city of Erie, forcing officials to declare an emergency.
Residents shared stunning photos of the whiteout on social media, with meteorologists attributing the 58 inches (147 centimeters) of snow that fell over Christmas Day, Monday, to 5 pm on Tuesday to icy winds blowing over the adjoining Lake Erie, one of North America's Great Lakes.
More snow was expected at a rate of up to an inch or two per hour as residents were warned to stay off the roads.
Pennsylvania Governor Tom Wolf announced that the National Guard was "providing high clearance all-terrain military vehicles to aid local agencies with medical emergency and law enforcement response."
According to data from the National Weather Service, the 34 inches of snow that fell on December 25 was the highest the city had ever recorded, eclipsing the previous high of 20 inches on November 22, 1956.
"The crews are out, but quite simply they can't keep up with the amount of snow that's falling," said Matt Exley, a local emergency official on a Facebook live post.
Erie has received 97 inches of snow in December, making it the snowiest month in the city's history -- which usually averages about 100 inches of snow in an entire season.
Unusually low temperatures were also recorded in the US northern Atlantic states.
In New York, weather authorities told residents to expect temperatures of between minus 12.7 C and minus 6.6 C through Saturday, which they described as "well below the normal."