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An intense cold spell has seized an intense and prolonged cold spell, with thermometers lingering in the minus 20 to minus 40 Celsius range for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature since 1975.

Prolonged Freeze Below -40C

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights below -40C, with Mayo plunging to -50.4C at the start of the week. Whitehorse similarly reported a series of ten nights when temperatures dropped below -30C.

The deep freeze spread farther south over the festive period. Christmas night saw Edmonton's temperatures plummet below minus 28C.

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

Likely to Linger into the New Year

This harsh winter weather is expected to continue through the start of January. Officials have warned that the Yukon could face electricity outages over the next several days, as the system endures record-high pressure from historically high electricity consumption.

The prolonged chill has been caused by a stationary polar vortex over Canada for much of December, enabling a surge of icy Arctic winds to descend. In the coming week, forecasts indicate this cold air will pull back northward 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 their warmest Christmas Day on record 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. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte similarly saw thermometers rise past the 25C mark.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue on December 26th and into the weekend, with atypical high temperatures expected to spread across the southeastern US in the coming days.

The unseasonable temperatures are powered by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. 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. Descending air compresses and adiabatically warms, enabling abnormally high temperatures to develop.