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An intense cold spell has seized a bitter and extended period of frigid weather, with temperatures hovering between -20C and -40C for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading in nearly five decades.

Consecutive Nights in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured over two straight weeks of nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C on Monday. Whitehorse also recorded 10 nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south over the festive period. Christmas night saw Edmonton's temperatures plummet below minus 28C.

The day after Christmas was forecast to deliver readings no higher than -20 Celsius across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger For Days to Come

This harsh winter weather is expected to continue 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 historically high electricity consumption.

The prolonged chill has been caused by the Arctic vortex settling over Canada for much of December, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Dramatic Difference Compared to Stateside Temperatures

Conversely, sections of America recorded historically high temperatures for Christmas as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May than late December.

Several states set Christmas Day temperature records. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Fuels Warmth

Above-average warmth is expected to continue for the remainder of the week and beyond, with unseasonable heat forecast to sweep into the south-eastern states later in the week.

The unseasonable temperatures are powered by a strong upper-level ridge reaching from the arid southwest across the continent, creating a heat-dome effect. 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.