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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 multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in nearly five decades.

Enduring Chill Below -40C

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. The capital, Whitehorse, likewise saw 10 nights when temperatures dropped below -30C.

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

Boxing Day was expected to bring lows of at least -20C across many regions, encompassing cities from Edmonton to Quebec.

Expected to Continue For Days to Come

This harsh winter weather is expected to continue through the start of January. Authorities have cautioned about potential power failures in the Yukon over the next several days, 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. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across the United States and penetrate southern Canadian regions.

Dramatic Difference to American Heat

In stark contrast, parts of the US experienced the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. For numerous locations, the weather resembled a spring day in April or May instead of the heart of winter.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

High-Pressure System Sustains High Temperatures

Warmer-than-normal conditions are forecast to last 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 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 blanketing a significant part of the landmass, 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.