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An intense cold spell has seized an intense and prolonged cold spell, with readings persisting in the minus 20 to minus 40 Celsius range for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in half a century.

Prolonged Freeze in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C on Monday. The capital, Whitehorse, likewise saw ten separate nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C through a wide swath, from Edmonton in the west to Quebec in the east.

Forecast to Persist For Days to Come

The frigid conditions are predicted to linger into the new year. There are warnings of possible electrical grid strain in Yukon territory soon, as the system endures record-high pressure from historically high electricity consumption.

This extended freeze is the result of the Arctic vortex settling across the northern part of the continent this month, allowing bitter Arctic air to spill south. In the coming week, forecasts indicate this cold air will pull back northward slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Stark Contrast to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. Across wide regions, the atmosphere was more akin to late spring than late December.

A number of states broke historical records for December 25th warmth. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, topping the prior high mark of 22 degrees established over forty years ago. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue through Boxing Day and the days ahead, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

The unseasonable temperatures are powered by a robust atmospheric ridge stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. This setup creates an extensive zone of high atmospheric pressure blanketing a significant part of the landmass, which holds warm air close to the ground. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.