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Northern Canada has been gripped by an intense and prolonged cold spell, with temperatures hovering between -20C and -40C for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature since 1975.

Consecutive Nights in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured 16 consecutive nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C earlier this week. The capital, Whitehorse, likewise saw a series of ten nights when temperatures dropped below -30C.

The bitter chill extended its reach south during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

Boxing Day was expected to bring minimum temperatures of at least minus 20C across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue Through Early January

This harsh winter weather is expected to continue through the start of January. There are warnings of possible electrical grid strain in Yukon territory soon, as the system endures record-high pressure from peak power usage levels.

The lengthy cold snap originates from a stationary polar vortex over Canada for much of December, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over the United States and penetrate southern Canadian regions.

Pronounced Disparity with US Warmth

In stark contrast, parts of the US experienced 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 instead of the heart of winter.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

Heat-Dome Effect Drives the Heat

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with atypical high temperatures expected to spread into the south-eastern states later in the week.

The unseasonable temperatures are powered by a strong upper-level ridge reaching from the arid southwest across the continent, creating a heat-dome effect. This pattern establishes a broad area of high pressure across much of the continent, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.