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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, representing its most frigid December day since 1975.

Prolonged Freeze Below -40C

Meanwhile, Mayo and Dawson endured sixteen nights in a row below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. Whitehorse similarly reported a series of ten nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver readings no higher than -20 Celsius across many regions, from Edmonton in the west to Quebec in the east.

Expected to Continue into the New Year

The frigid conditions are predicted to linger for the foreseeable future. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as the system endures record-high pressure from record-high energy demand.

This extended freeze is the result of a stationary polar vortex above Canadian territory through December, 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.

Dramatic Difference with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw historically high temperatures for Christmas as temperatures soared about 15-30C above the seasonal average. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, surpassing the previous peak of 22C set in 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Atmospheric Ridge Drives the Heat

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with abnormal warmth projected to move through the American Southeast soon.

The unseasonable temperatures are powered by a robust atmospheric ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. This pattern establishes a broad area of high pressure across much of the continent, which holds warm air close to the ground. Descending air compresses and adiabatically warms, enabling abnormally high temperatures to develop.