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An intense cold spell has seized a severe and lengthy Arctic outbreak, with thermometers lingering between -20C and -40C for weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in nearly five decades.

Prolonged Freeze Below -40C

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C earlier this week. Whitehorse also recorded ten separate nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward over the festive period. 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.

Forecast to Persist For Days to Come

The severe cold is forecast to persist through the start of January. Officials have warned that the Yukon could face electricity outages soon, as its energy infrastructure faces unprecedented demand from historically high electricity consumption.

The lengthy cold snap originates from the Arctic vortex settling across the northern part of the continent this month, allowing bitter Arctic air to spill south. The frigid dome is projected to gradually withdraw north allowing more temperate air from the Pacific to sweep across the US and into parts of southern Canada.

Dramatic Difference with US Warmth

In stark contrast, parts of the US experienced the hottest December 25th in their history 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 also logged readings above 25 degrees Celsius.

Atmospheric Ridge Sustains High Temperatures

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

This heat is being driven by a strong upper-level ridge reaching from the arid southwest across the continent, establishing a classic heat-dome pattern. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, which holds warm air close to the ground. Sinking atmospheric air undergoes compression and additional heating, fostering the buildup of exceptional warmth.