Extreme cold in Canada has disrupted flights and school classes, caused widespread power outages and created havoc on roads.
Temperatures as low as minus 50 degrees Celsius with a wind chill - colder than the surface of Mars - plunged the western Prairies region into a deep freeze, heightening risks of frostbite and hypothermia.
Toronto, Montreal and the capital Ottawa braced for a flash freeze on Monday with temperatures forecast to drop as much as 40 degrees in less than 24 hours, after locals awoke to unusually warm temperatures (above freezing) and rain.
Environment Canada warned of "treacherous" travelling conditions.
"Extreme caution is advised for people heading outdoors," the government agency said. "Exposed skin may freeze in less than five minutes."
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One in 10 flights from Toronto's international airport were cancelled. And hundreds of car accidents in central Ontario and Quebec provinces were blamed on slick roads and fierce winds.
This comes after Toronto area residents continue to recover from an ice storm that left 300,000 hydro customers in the dark over the Christmas holidays.
More than 30,000 residents of the Atlantic island province of Newfoundland meanwhile were still without power after a blizzard knocked out electricity last week. At its peak, the blackout covered the entire island, affecting nearly 200,000 residents.
