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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with readings persisting between -20C and -40C for weeks. On Tuesday, Braeburn in the Yukon recorded -55.7C, marking its chilliest December reading in half a century.

Enduring Chill in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured 16 consecutive nights colder than minus 40 degrees, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse similarly reported a series of ten nights when temperatures dropped below -30C.

The deep freeze spread farther south through Christmas week. 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, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue For Days to Come

The severe cold is forecast to persist for the foreseeable future. There are warnings of possible electrical grid strain in Yukon territory soon, as the system endures record-high pressure from record-high energy demand.

The prolonged chill has been caused by the Arctic vortex settling above Canadian territory through December, allowing bitter Arctic air to spill south. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across the United States and penetrate southern Canadian regions.

Dramatic Difference to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. Across wide regions, the atmosphere was more akin to late spring than late December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, exceeding the old record of 22C from 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

High-Pressure System Fuels Warmth

Above-average warmth is expected to continue for the remainder of the week and beyond, with unseasonable heat forecast to sweep through the American Southeast soon.

This heat is being driven by a robust atmospheric ridge reaching from the arid southwest across the continent, creating a heat-dome effect. Such a configuration results in a widespread high-pressure system over a large portion of North America, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, fostering the buildup of exceptional warmth.