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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with readings persisting in the minus 20 to minus 40 Celsius range for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature since 1975.

Consecutive Nights Below -40C

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. Whitehorse also recorded 10 nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward during the holiday season. 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.

Likely to Linger Through Early January

This harsh winter weather is expected to continue into the new year. Authorities have cautioned about potential power failures in the Yukon soon, as its energy infrastructure faces unprecedented demand from record-high energy demand.

The prolonged chill has been caused by the Arctic vortex settling over Canada for much of December, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced the hottest December 25th in their history as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring 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, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

Heat-Dome Effect Sustains High Temperatures

Above-average warmth is expected to continue 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 strong upper-level 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, which holds warm air close to the ground. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.