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An intense cold spell has seized a bitter and extended period of frigid weather, with readings persisting between -20C and -40C for an extended duration. On Tuesday, Braeburn in the Yukon recorded -55.7C, representing its most frigid December day since 1975.

Prolonged Freeze Below -40C

Similarly, the communities of Mayo and Dawson experienced 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 also recorded ten separate nights when the cold dipped under -30 Celsius.

The bitter chill extended its reach south through Christmas week. Christmas night saw Edmonton's temperatures plummet below minus 28C.

December 26th was anticipated to usher in readings no higher than -20 Celsius through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger into the New Year

This harsh winter weather is expected to continue through the start of January. 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 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 gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Pronounced Disparity with US Warmth

Conversely, sections of America recorded 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

Above-average warmth is expected to continue on December 26th and into the weekend, with unseasonable heat forecast to sweep through the American Southeast soon.

The warmth has been fuelled by a strong upper-level ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system 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.