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An intense cold spell has seized a bitter and extended period of frigid weather, with thermometers lingering from 20 to 40 degrees below zero for an extended duration. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in half a century.

Enduring Chill of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights below -40C, with Mayo plunging to -50.4C on Monday. The capital, Whitehorse, likewise saw a series of ten 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.

Boxing Day was expected to bring minimum temperatures of at least minus 20C across many regions, from Edmonton in the west to Quebec in the east.

Likely to Linger 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 in the coming days, as the territory’s power grid comes under strain from peak power usage levels.

This extended freeze is the result of 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 America and reach into portions of southern Canada.

Dramatic Difference with US Warmth

In stark contrast, parts of the US experienced the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. For numerous locations, the weather resembled a spring day in 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. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

High-Pressure System Drives the Heat

Above-average warmth is expected to continue for the remainder of the week and beyond, with atypical high temperatures expected to spread through the American Southeast soon.

The warmth has been fuelled by a strong upper-level ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. Such a configuration results in a widespread high-pressure system across much of the continent, trapping warm air near the surface. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.