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An intense cold spell has seized a bitter and extended period of frigid weather, with readings persisting between -20C and -40C for weeks. 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

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 on Monday. Whitehorse also recorded a series of ten nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward over the festive period. Christmas night saw Edmonton's temperatures plummet below minus 28C.

The day after Christmas was forecast to deliver readings no higher than -20 Celsius through a wide swath, encompassing cities from Edmonton to Quebec.

Expected to Continue into the New Year

This harsh winter weather is expected to continue through the start of January. Authorities have cautioned about potential power failures in the Yukon over the next several days, as the territory’s power grid comes under strain from historically high electricity consumption.

The lengthy cold snap originates from a stationary polar vortex above Canadian territory through December, which funnels frigid northern air southward. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Dramatic Difference with US Warmth

Conversely, sections of America recorded historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Drives the Heat

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with abnormal warmth projected to move across the southeastern US in the coming days.

The warmth has been fuelled by a powerful high-altitude ridge extending from the desert south-west towards the north and east, creating a heat-dome effect. This pattern establishes a broad area of high pressure over a large portion of North America, trapping warm air near the surface. Descending air compresses and adiabatically warms, enabling abnormally high temperatures to develop.