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An intense cold spell has seized a bitter and extended period of frigid weather, with readings persisting in the minus 20 to minus 40 Celsius range for weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in half a century.

Enduring Chill of Extreme Cold

Meanwhile, Mayo and Dawson endured over two straight weeks of nights colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius earlier this week. Whitehorse also recorded 10 nights when readings fell to minus 30 degrees or lower.

The bitter chill extended its reach south over the festive period. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

The day after Christmas was forecast to deliver lows of at least -20C across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Forecast to Persist into the New Year

The frigid conditions are predicted to linger through the start of January. There are warnings of possible electrical grid strain in Yukon territory in the coming days, as its energy infrastructure faces unprecedented demand from record-high energy demand.

This extended freeze is the result of the Arctic vortex settling across the northern part of the continent this month, allowing bitter Arctic air to spill south. In the coming week, forecasts indicate this cold air will pull back northward allowing more temperate air from the Pacific to sweep across the United States and penetrate southern Canadian regions.

Stark Contrast with US Warmth

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. For numerous locations, the weather resembled a spring day in April or May than late December.

Multiple states established new Christmas temperature highs. In Oklahoma, Oklahoma City hit 25C on Tuesday, exceeding the old record of 22C from 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Atmospheric Ridge Drives the Heat

Above-average warmth is expected to continue for the remainder of the week and beyond, with atypical high temperatures expected to spread through the American Southeast soon.

The unseasonable temperatures are powered by a strong upper-level ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system over a large portion of North America, which holds warm air close to the ground. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.