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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with thermometers lingering between -20C and -40C 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 in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured over two straight weeks of nights dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius on Monday. Whitehorse also recorded 10 nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward over the festive period. Christmas night saw Edmonton's temperatures plummet below minus 28C.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C in numerous areas, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger Through Early January

The severe cold is forecast to persist for the foreseeable future. Officials have warned that the Yukon could face electricity outages soon, as the territory’s power grid comes under strain from historically high electricity consumption.

The lengthy cold snap originates from a stationary polar vortex across the northern part of the continent this month, allowing bitter Arctic air to spill south. 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 historically high temperatures for Christmas 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. In Oklahoma, Oklahoma City hit 25C on Tuesday, topping the prior high mark of 22 degrees established over forty years ago. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

High-Pressure System Fuels Warmth

Unseasonable heat is predicted to persist on December 26th and into the weekend, with atypical high temperatures expected to spread through the American Southeast soon.

This heat is being driven by a robust atmospheric ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. This pattern establishes a broad area of high pressure across much of the continent, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.