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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, with temperatures hovering in the minus 20 to minus 40 Celsius range for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, its coldest December temperature in nearly five decades.

Prolonged Freeze Below -40C

Similarly, the communities of Mayo and Dawson experienced 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 10 nights when temperatures dropped below -30C.

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

Boxing Day was expected to bring lows of at least -20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue into the New Year

The severe cold is forecast to persist into the new year. Officials have warned that the Yukon could face electricity outages over the next several days, as the territory’s power grid comes under strain from historically high electricity consumption.

This extended freeze is the result of the polar vortex remaining anchored over Canada for much of December, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north slowly, permitting warmer Pacific winds to flow over the US and into parts of southern Canada.

Stark Contrast with US Warmth

Conversely, sections of America recorded historically high temperatures for Christmas as the mercury climbed roughly 15 to 30 degrees above typical averages. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

Multiple states established new Christmas temperature highs. The capital of Oklahoma soared to 25C on Christmas Day, exceeding the old record of 22C from 1982. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

Atmospheric Ridge Fuels Warmth

Unseasonable heat is predicted to persist on December 26th and into the weekend, with atypical high temperatures expected to spread into the south-eastern states later in the week.

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 blanketing a significant part of the landmass, trapping warm air near the surface. As air sinks through the atmosphere, it compresses and heats further, enabling abnormally high temperatures to develop.