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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with thermometers lingering between -20C and -40C for an extended duration. On Tuesday, Braeburn in the Yukon recorded -55.7C, its coldest December temperature since 1975.

Consecutive Nights of Extreme Cold

In addition, the locales of Mayo and Dawson suffered through over two straight weeks of nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C earlier this week. Whitehorse similarly reported ten separate nights when readings fell to minus 30 degrees or lower.

This Arctic air mass pushed further southward during the holiday season. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

Boxing Day was expected to bring minimum temperatures of at least minus 20C through a wide swath, encompassing cities from Edmonton to Quebec.

Likely to Linger into the New Year

The severe cold is forecast to persist for the foreseeable future. Authorities have cautioned about potential power failures in the Yukon soon, as its energy infrastructure faces unprecedented demand from record-high energy demand.

This extended freeze is the result of the Arctic vortex settling over Canada for much of December, enabling a surge of icy Arctic winds to descend. In the coming week, forecasts indicate this cold air will pull back northward slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Stark Contrast to American Heat

Conversely, sections of America recorded the hottest December 25th in their history 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.

A number of states broke historical records for December 25th warmth. 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 also logged readings above 25 degrees Celsius.

Heat-Dome Effect Drives the Heat

Warmer-than-normal conditions are forecast to last 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 stretching from the southwestern deserts northward and eastward, establishing a classic heat-dome pattern. This pattern establishes a broad area of high pressure over a large portion of North America, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.