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A prolonged deep freeze has enveloped a bitter and extended period of frigid weather, with temperatures hovering between -20C and -40C for an extended duration. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, representing its most frigid December day since 1975.

Consecutive Nights of Extreme Cold

Meanwhile, Mayo and Dawson endured 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 on Monday. The capital, Whitehorse, likewise saw 10 nights when temperatures dropped below -30C.

This Arctic air mass pushed further southward over the festive period. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C across many regions, from Edmonton in the west to Quebec in the east.

Forecast to Persist Through Early January

The severe cold is forecast to persist through the start of January. Officials have warned that the Yukon could face electricity outages soon, as the system endures record-high pressure from record-high energy demand.

The prolonged chill has been caused by a stationary polar vortex over Canada for much of December, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across America and reach into portions 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. Across wide regions, the atmosphere was more akin to late spring instead of the heart of winter.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, 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.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue through Boxing Day and the days ahead, with abnormal warmth projected to move into the south-eastern states later in the week.

This heat is being driven by a powerful high-altitude ridge reaching from the arid southwest across the continent, 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.