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An intense cold spell has seized a severe and lengthy Arctic outbreak, with readings persisting between -20C and -40C for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in nearly five decades.

Consecutive Nights in the Deep Minus Forties

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius earlier this week. The capital, Whitehorse, likewise saw 10 nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward over the festive period. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver lows of at least -20C across many regions, from Edmonton in the west to Quebec in the east.

Expected to Continue For Days to Come

The severe cold is forecast to persist through the start of January. Officials have warned that the Yukon could face electricity outages soon, as the system endures record-high pressure from peak power usage levels.

This extended freeze is the result of the polar vortex remaining anchored over Canada for much of December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Dramatic Difference Compared to Stateside Temperatures

Meanwhile, in a dramatic contrast, areas of the United States saw their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. Across wide regions, the atmosphere was more akin to late spring than late December.

Several states set Christmas Day temperature records. In Oklahoma, Oklahoma City hit 25C on Tuesday, topping the prior high mark of 22 degrees established over forty years ago. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

High-Pressure System Sustains High Temperatures

Unseasonable heat is predicted to persist on December 26th and into the weekend, with abnormal warmth projected to move through the American Southeast soon.

The warmth has been fuelled by a robust atmospheric ridge reaching from the arid southwest across the continent, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system over a large portion of North America, which holds warm air close to the ground. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.