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Northern Canada has been gripped by a bitter and extended period of frigid weather, with readings persisting 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.

Prolonged Freeze in the Deep Minus Forties

In addition, the locales of Mayo and Dawson suffered through over two straight weeks of 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 readings fell to minus 30 degrees or lower.

The bitter chill extended its reach south during the holiday season. 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, from Edmonton in the west to Quebec in the east.

Forecast to Persist into the New Year

The severe cold is forecast to persist into the new year. Authorities have cautioned about potential power failures in the Yukon over the next several days, as its energy infrastructure faces unprecedented demand from record-high energy demand.

The prolonged chill has been caused by the polar vortex remaining anchored 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 United States and penetrate southern Canadian regions.

Dramatic Difference Compared to Stateside Temperatures

Conversely, sections of America recorded the hottest December 25th in their history as readings skyrocketed 15 to 30 degrees Celsius above normal. 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. 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 similarly saw thermometers rise past the 25C mark.

High-Pressure System Sustains High Temperatures

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with abnormal warmth projected to move through the American Southeast soon.

This heat is being driven 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, trapping warm air near the surface. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.