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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with thermometers lingering between -20C and -40C for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading since 1975.

Prolonged Freeze in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights colder than minus 40 degrees, with Mayo plunging to -50.4C at the start of the week. The capital, Whitehorse, likewise saw a series of ten nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south through Christmas week. Christmas night saw Edmonton's temperatures plummet below minus 28C.

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

Forecast to Persist into the New Year

This harsh winter weather is expected to continue through the start of January. There are warnings of possible electrical grid strain in Yukon territory in the coming days, as the territory’s power grid comes under strain from historically high electricity consumption.

The lengthy cold snap originates from the polar vortex remaining anchored across the northern part of the continent this month, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north slowly, permitting warmer Pacific winds to flow over America and reach into portions of southern Canada.

Stark Contrast to American Heat

In stark contrast, parts of the US experienced historically high temperatures for Christmas as temperatures soared about 15-30C above the seasonal average. Across wide regions, the atmosphere was more akin to late spring instead of the heart of winter.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Metropolitan areas such as Austin, Dallas, and Charlotte also logged readings above 25 degrees Celsius.

Heat-Dome Effect Fuels Warmth

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with unseasonable heat forecast to sweep into the south-eastern states later in the week.

The warmth has been fuelled by a powerful high-altitude ridge extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. As air sinks through the atmosphere, it compresses and heats further, fostering the buildup of exceptional warmth.