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An intense cold spell has seized a severe and lengthy Arctic outbreak, with readings persisting from 20 to 40 degrees below zero for multiple weeks. 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 Mayo plunging to -50.4C earlier this week. Whitehorse also recorded ten separate nights when the cold dipped under -30 Celsius.

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

December 26th was anticipated to usher in lows of at least -20C across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger into the New Year

This harsh winter weather is expected to continue into the new year. Authorities have cautioned about potential power failures in the Yukon in the coming days, as the territory’s power grid comes under strain from record-high energy demand.

This extended freeze is the result of a stationary polar vortex 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 allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Stark Contrast with US Warmth

Conversely, sections of America recorded 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.

Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Drives the Heat

Above-average warmth is expected to continue on December 26th and into the weekend, with abnormal warmth projected to move through the American Southeast soon.

The warmth has been fuelled by a powerful high-altitude ridge extending from the desert south-west towards the north and east, 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.