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An intense cold spell has seized an intense and prolonged cold spell, with temperatures hovering from 20 to 40 degrees below zero for an extended duration. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in half a century.

Enduring Chill 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 plunging to -50.4C earlier this week. The capital, Whitehorse, likewise saw ten separate 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.

December 26th was anticipated to usher in lows of at least -20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Forecast to Persist Through Early January

The frigid conditions are predicted to linger into the new year. Authorities have cautioned about potential power failures in the Yukon soon, as the territory’s power grid comes under strain from record-high energy demand.

This extended freeze is the result of a stationary polar vortex across the northern part of the continent this month, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Dramatic Difference to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May than late December.

Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

High-Pressure System Drives the Heat

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with abnormal warmth projected to move into the south-eastern states later in the week.

The warmth has been fuelled by a robust atmospheric ridge extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. This setup creates an extensive zone of high atmospheric 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.