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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with readings persisting from 20 to 40 degrees below zero for an extended duration. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading since 1975.

Enduring Chill of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights below -40C, with Mayo plunging to -50.4C on Monday. Whitehorse similarly reported a series of ten nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward through Christmas week. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring minimum temperatures of at least minus 20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger Through Early January

The severe cold is forecast to persist into the new year. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as the territory’s power grid comes under strain from record-high energy demand.

This extended freeze is the result of the polar vortex remaining anchored above Canadian territory through December, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across the United States and penetrate southern Canadian regions.

Pronounced Disparity with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May instead of the heart of winter.

A number of states broke historical records for December 25th warmth. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, surpassing the previous peak of 22C set in 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue for the remainder of the week and beyond, with abnormal warmth projected to move into the south-eastern states later in the week.

The unseasonable temperatures are powered by a strong upper-level ridge extending from the desert south-west towards the north and east, 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.