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An intense cold spell has seized an intense and prolonged cold spell, with temperatures hovering from 20 to 40 degrees below zero for an extended duration. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day in half a century.

Consecutive Nights of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded 10 nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward through Christmas week. Christmas night saw Edmonton's temperatures plummet below minus 28C.

Boxing Day was expected to bring lows of at least -20C across many regions, from Edmonton in the west to Quebec in the east.

Expected to Continue For Days to Come

The severe cold is forecast to persist into the new year. There are warnings of possible electrical grid strain in Yukon territory over the next several days, as the system endures record-high pressure from peak power usage levels.

The lengthy cold snap originates from a stationary polar vortex over Canada for much of December, enabling a surge of icy Arctic winds to descend. 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.

Pronounced Disparity with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw their warmest Christmas Day on record as temperatures soared about 15-30C above the seasonal average. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Sustains High Temperatures

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 robust atmospheric ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system over a large portion of North America, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.