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An intense cold spell has seized a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for an extended duration. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature in nearly five decades.

Enduring Chill in the Deep Minus Forties

Meanwhile, Mayo and Dawson endured sixteen nights in a row dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. Whitehorse similarly reported 10 nights when readings fell to minus 30 degrees or lower.

The deep freeze spread farther south during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

December 26th was anticipated to usher in minimum temperatures of at least minus 20C across many regions, encompassing cities from Edmonton to Quebec.

Expected to Continue Through Early January

This harsh winter weather is expected to continue 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 prolonged chill has been caused by a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. In the coming week, forecasts indicate this cold air will pull back northward gradually, enabling milder Pacific air to move across the US and into parts of southern Canada.

Stark Contrast to American Heat

In stark contrast, parts of the US experienced their warmest Christmas Day on record as the mercury climbed roughly 15 to 30 degrees above typical averages. In many areas, conditions felt more typical of April or May rather than the end of December.

Multiple states established new Christmas temperature highs. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, topping the prior high mark of 22 degrees established over forty years ago. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

Heat-Dome Effect Sustains High Temperatures

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, creating a heat-dome effect. This setup creates an extensive zone of high atmospheric pressure across much of the continent, trapping warm air near the surface. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.