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Northern Canada has been gripped by an intense and prolonged cold spell, with readings persisting in the minus 20 to minus 40 Celsius range for an extended duration. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day in nearly five decades.

Prolonged Freeze Below -40C

In addition, the locales of Mayo and Dawson suffered through over two straight weeks of nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C on Monday. Whitehorse similarly reported 10 nights when the cold dipped under -30 Celsius.

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

December 26th was anticipated to usher in lows of at least -20C across many regions, from Edmonton in the west to Quebec in the east.

Forecast to Persist For Days to Come

The severe cold is forecast to persist for the foreseeable future. Officials have warned that the Yukon could face electricity outages over the next several days, as the territory’s power grid comes under strain from record-high energy demand.

The lengthy cold snap originates from the polar vortex remaining anchored over Canada for much of December, enabling a surge of icy Arctic winds to descend. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across the United States and penetrate southern Canadian regions.

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. Across wide regions, the atmosphere was more akin to late spring rather than the end of December.

Several states set Christmas Day temperature records. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte similarly saw thermometers rise past the 25C mark.

Atmospheric Ridge Fuels Warmth

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with abnormal warmth projected to move across the southeastern US in the coming days.

The warmth has been fuelled by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.