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A prolonged deep freeze has enveloped a bitter and extended period of frigid weather, with readings persisting from 20 to 40 degrees below zero for multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature since 1975.

Consecutive Nights of Extreme Cold

Similarly, the communities of Mayo and Dawson experienced sixteen nights in a row colder than minus 40 degrees, with Mayo plunging to -50.4C at the start of the week. The capital, Whitehorse, likewise saw 10 nights when temperatures dropped below -30C.

The bitter chill extended its reach south 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 across many regions, from Edmonton in the west to Quebec in the east.

Expected to Continue into the New Year

The frigid conditions are predicted to linger for the foreseeable future. There are warnings of possible electrical grid strain in Yukon territory in the coming days, as the system endures record-high pressure from peak power usage levels.

The prolonged chill has been caused by the polar vortex remaining anchored across the northern part of the continent this month, which funnels frigid northern air southward. Next week, the cold air mass is expected to retreat north gradually, enabling milder Pacific air to move across the US and into parts of southern Canada.

Pronounced Disparity to American Heat

Meanwhile, in a dramatic contrast, areas of the United States saw the hottest December 25th in their history as temperatures soared about 15-30C above the seasonal average. In many areas, conditions felt more typical of April or May than late December.

Several states set Christmas Day temperature records. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, topping the prior high mark of 22 degrees established over forty years ago. Urban centers like Austin, Dallas, and Charlotte, North Carolina were also among those that recorded temperatures above 25C.

High-Pressure System Drives the Heat

Unseasonable heat is predicted to persist for the remainder of the week and beyond, with atypical high temperatures expected to spread through the American Southeast soon.

This heat is being driven by a strong upper-level ridge extending from the desert south-west towards the north and east, which generates a heat-dome phenomenon. Such a configuration results in a widespread high-pressure system across much of the continent, trapping warm air near the surface. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.