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An intense cold spell has seized a severe and lengthy Arctic outbreak, with temperatures hovering from 20 to 40 degrees below zero for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, representing its most frigid December day in nearly five decades.

Prolonged Freeze of Extreme Cold

Meanwhile, Mayo and Dawson endured 16 consecutive nights below -40C, with Mayo plunging to -50.4C earlier this week. Whitehorse similarly reported ten separate nights when the cold dipped under -30 Celsius.

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 through a wide swath, from Edmonton in the west to Quebec in the east.

Likely to Linger For Days to Come

The severe cold is forecast to persist 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 peak power usage levels.

The lengthy cold snap originates from the polar vortex remaining anchored above Canadian territory through December, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Dramatic Difference to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May instead of the heart of winter.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Sustains High Temperatures

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with atypical high temperatures expected to spread into the south-eastern states later in the week.

The unseasonable temperatures are powered by a powerful high-altitude ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. This setup creates an extensive zone of high atmospheric pressure over a large portion of North America, trapping warm air near the surface. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.