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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, representing its most frigid December day since 1975.

Consecutive Nights in the Deep Minus Forties

In addition, the locales of Mayo and Dawson suffered through 16 consecutive nights dipping under the minus 40 Celsius threshold, with Mayo plunging to -50.4C on Monday. Whitehorse similarly reported a series of ten nights when the cold dipped under -30 Celsius.

The deep freeze spread farther south through Christmas week. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver lows of at least -20C across many regions, including Edmonton, Montreal, Ottawa and Quebec.

Forecast to Persist into the New Year

This harsh winter weather is expected to continue through the start of January. 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 record-high energy demand.

The prolonged chill has been caused by a stationary polar vortex 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 allowing more temperate air from the Pacific to sweep across America and reach into portions of southern Canada.

Dramatic Difference to American Heat

Conversely, sections of America recorded historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. In many areas, conditions felt more typical of April or May than late December.

Several states set Christmas Day temperature records. The capital of Oklahoma soared to 25C on Christmas Day, 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

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

The warmth has been fuelled by a strong upper-level 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, which holds warm air close to the ground. Sinking atmospheric air undergoes compression and additional heating, enabling abnormally high temperatures to develop.