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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with thermometers lingering in the minus 20 to minus 40 Celsius range for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in half a century.

Enduring Chill of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced sixteen nights in a row colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius earlier this week. Whitehorse similarly reported ten separate nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south during the holiday season. 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 across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger Through Early January

The frigid conditions are predicted to linger through the start of January. Officials have warned that the Yukon could face electricity outages soon, as its energy infrastructure faces unprecedented demand from peak power usage levels.

The prolonged chill has been caused by the Arctic vortex settling above Canadian territory through December, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north slowly, permitting warmer Pacific winds to flow over America and reach into portions of southern Canada.

Pronounced Disparity Compared to Stateside Temperatures

In stark contrast, parts of the US experienced historically high temperatures for Christmas as temperatures soared about 15-30C above the seasonal average. For numerous locations, the weather resembled a spring day in April or May than late December.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Metropolitan areas such as Austin, Dallas, and Charlotte similarly saw thermometers rise past the 25C mark.

High-Pressure System Drives the Heat

Above-average warmth is expected to continue through Boxing Day and the days ahead, with abnormal warmth projected to move through the American Southeast soon.

The warmth has been fuelled by a powerful high-altitude ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. This setup creates an extensive zone of high atmospheric pressure blanketing a significant part of the landmass, which holds warm air close to the ground. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.