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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with thermometers lingering between -20C and -40C for multiple weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature in nearly five decades.

Enduring Chill Below -40C

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row colder than minus 40 degrees, with Mayo experiencing a low of -50.4C 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 over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

Boxing Day was expected to bring 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

This harsh winter weather is expected to continue into the new year. Authorities have cautioned about potential power failures in the Yukon over the next several days, as the territory’s power grid comes under strain from peak power usage levels.

The lengthy cold snap originates from a stationary polar vortex across the northern part of the continent this month, which funnels frigid northern air southward. 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.

Pronounced Disparity with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw 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 rather than the end of December.

Multiple states established new Christmas temperature highs. 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 Sustains High Temperatures

Above-average warmth is expected to continue on December 26th and into the weekend, with unseasonable heat forecast to sweep through the American Southeast soon.

The warmth has been fuelled by a robust atmospheric ridge reaching from the arid southwest across the continent, which generates a heat-dome phenomenon. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, trapping warm air near the surface. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.