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An intense cold spell has seized a bitter and extended period of frigid weather, with thermometers lingering in the minus 20 to minus 40 Celsius range for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in nearly five decades.

Prolonged Freeze Below -40C

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights 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 readings fell to minus 30 degrees or lower.

The bitter chill extended its reach south during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver lows of at least -20C across many regions, encompassing cities from Edmonton to Quebec.

Expected to Continue into the New Year

The severe cold is forecast to persist for the foreseeable future. Authorities have cautioned about potential power failures in the Yukon in the coming days, as the territory’s power grid comes under strain 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. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring instead of the heart of winter.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Atmospheric Ridge Fuels Warmth

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with atypical high temperatures expected to spread through the American Southeast soon.

The warmth has been fuelled by a strong upper-level ridge reaching from the arid southwest across the continent, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system over a large portion of North America, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.