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An intense cold spell has seized a bitter and extended period of frigid weather, with thermometers lingering from 20 to 40 degrees below zero for weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, representing its most frigid December day in half a century.

Enduring Chill of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced 16 consecutive nights below -40C, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded a series of ten nights when temperatures dropped below -30C.

The bitter chill extended its reach south over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

The day after Christmas was forecast to deliver minimum temperatures of at least minus 20C through a wide swath, including Edmonton, Montreal, Ottawa and Quebec.

Expected to Continue Through Early January

The severe cold is forecast to persist through the start of January. Officials have warned that the Yukon could face electricity outages in the coming days, as the system endures record-high pressure from peak power usage levels.

This extended freeze is the result of the polar vortex remaining anchored 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 gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May than late December.

Several states set Christmas Day temperature records. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, exceeding the old record of 22C from 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

Heat-Dome Effect Fuels Warmth

Warmer-than-normal conditions are forecast to last on December 26th and into the weekend, with atypical high temperatures expected to spread across the southeastern US in the coming days.

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. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, effectively capping warm air at lower altitudes. Sinking atmospheric air undergoes compression and additional heating, allowing unusually warm temperatures to build.