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An intense cold spell has seized a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, marking its chilliest December reading in half a century.

Prolonged Freeze Below -40C

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C earlier this week. Whitehorse similarly reported a series of ten nights when temperatures dropped below -30C.

The bitter chill extended its reach south during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring readings no higher than -20 Celsius 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 for the foreseeable future. Officials have warned that the Yukon could face electricity outages over the next several days, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.

The prolonged chill has been caused by the Arctic vortex settling across the northern part of the continent this month, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Pronounced Disparity Compared to Stateside Temperatures

Conversely, sections of America recorded the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May instead of the heart of winter.

Several states set Christmas Day temperature records. 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 also logged readings above 25 degrees Celsius.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue on December 26th and into the weekend, with atypical high temperatures expected to spread across the southeastern US in the coming days.

The warmth has been fuelled 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 blanketing a significant part of the landmass, trapping warm air near the surface. Descending air compresses and adiabatically warms, fostering the buildup of exceptional warmth.