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Northern Canada has been gripped by an intense and prolonged cold spell, with thermometers lingering 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, marking its chilliest December reading in half a century.

Consecutive Nights Below -40C

Meanwhile, Mayo and Dawson endured over two straight weeks of nights below -40C, with the temperature in Mayo bottoming out at -50.4 degrees Celsius earlier this week. Whitehorse also recorded ten separate nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward through Christmas week. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in lows of at least -20C through a wide swath, from Edmonton in the west to Quebec in the east.

Likely to Linger into the New Year

The frigid conditions are predicted to linger through the start of January. Officials have warned that the Yukon could face electricity outages soon, as its energy infrastructure faces unprecedented demand from peak power usage levels.

The prolonged chill has been caused by the Arctic vortex settling 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 United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

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 similarly saw thermometers rise past the 25C mark.

High-Pressure System Drives the Heat

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with abnormal warmth projected to move 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, creating a heat-dome effect. This setup creates an extensive zone of high atmospheric pressure across much of the continent, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.