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An intense cold spell has seized a bitter and extended period of frigid weather, with temperatures hovering 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.

Consecutive Nights Below -40C

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C on Monday. The capital, Whitehorse, likewise saw a series of ten nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward during the holiday season. Christmas night saw Edmonton's temperatures plummet below minus 28C.

December 26th was anticipated to usher in readings no higher than -20 Celsius through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Likely to Linger For Days to Come

The severe cold is forecast to persist through the start of January. There are warnings of possible electrical grid strain in Yukon territory 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 over Canada for much of December, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Dramatic Difference to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May than late December.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

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 across the southeastern US in the coming days.

This heat is being driven by a robust atmospheric ridge extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system blanketing a significant part of the landmass, 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.