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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering between -20C and -40C for an extended duration. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading in half a century.

Prolonged Freeze Below -40C

Meanwhile, Mayo and Dawson endured sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded ten separate nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south through Christmas week. On Christmas Day, overnight temperatures in Edmonton fell below -28C.

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

Forecast to Persist into the New Year

The frigid conditions are predicted to linger into the new year. Officials have warned that the Yukon could face electricity outages over the next several days, as its energy infrastructure faces unprecedented demand from record-high energy demand.

The lengthy cold snap originates from the Arctic vortex settling over Canada for much of December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Dramatic Difference Compared to Stateside Temperatures

Conversely, sections of America recorded the hottest December 25th in their history as readings skyrocketed 15 to 30 degrees Celsius above normal. In many areas, conditions felt more typical of April or May 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, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

Heat-Dome Effect Sustains High Temperatures

Warmer-than-normal conditions are forecast to last through Boxing Day and the days ahead, with abnormal warmth projected to move into the south-eastern states later in the week.

The warmth has been fuelled by a robust atmospheric 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 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, allowing unusually warm temperatures to build.