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Northern Canada has been gripped by a bitter and extended period of frigid weather, with thermometers lingering from 20 to 40 degrees below zero for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in nearly five decades.

Enduring Chill Below -40C

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. The capital, Whitehorse, likewise saw ten separate nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south over the festive period. 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 For Days to Come

The frigid conditions are predicted to linger through the start of January. Officials have warned that the Yukon could face electricity outages soon, as the system endures record-high pressure from peak power usage levels.

The prolonged chill has been caused by the polar vortex remaining anchored 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 US and into parts of southern Canada.

Stark Contrast Compared to Stateside Temperatures

In stark contrast, parts of the US experienced historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. In many areas, conditions felt more typical of April or May than late 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 also logged readings above 25 degrees Celsius.

Heat-Dome Effect Fuels Warmth

Above-average warmth is expected to continue on December 26th and into the weekend, with atypical high temperatures expected to spread into the south-eastern states later in the week.

This heat is being driven by a powerful high-altitude ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. Such a configuration results in a widespread high-pressure system across much of the continent, which holds warm air close to the ground. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.