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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with readings persisting between -20C and -40C for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature since 1975.

Prolonged Freeze in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights below -40C, with Mayo plunging to -50.4C earlier this week. Whitehorse similarly reported ten separate nights when readings fell to minus 30 degrees or lower.

The bitter chill extended its reach south through Christmas week. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in minimum temperatures of at least minus 20C through a wide swath, from Edmonton in the west to Quebec in the east.

Expected to Continue into the New Year

This harsh winter weather is expected to continue into the new year. There are warnings of possible electrical grid strain in Yukon territory soon, as the system endures record-high pressure from record-high energy demand.

The prolonged chill has been caused by a stationary polar vortex across the northern part of the continent this month, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Stark Contrast with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Drives the Heat

Warmer-than-normal conditions are forecast to last for the remainder of the week and beyond, with unseasonable heat forecast to sweep into the south-eastern states later in the week.

The unseasonable temperatures are powered by a robust atmospheric ridge reaching from the arid southwest across the continent, which generates a heat-dome phenomenon. This setup creates an extensive zone of high atmospheric pressure over a large portion of North America, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.