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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 multiple weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, representing its most frigid December day in half a century.

Enduring Chill Below -40C

Meanwhile, Mayo and Dawson endured sixteen nights in a row dipping under the minus 40 Celsius threshold, with Mayo experiencing a low of -50.4C on Monday. Whitehorse similarly reported 10 nights when the cold dipped under -30 Celsius.

This Arctic air mass pushed further southward over the festive period. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

Boxing Day was expected to bring minimum temperatures of at least minus 20C in numerous areas, encompassing cities from Edmonton to Quebec.

Forecast to Persist Through Early January

The severe cold is forecast to persist into the new year. Authorities have cautioned about potential power failures in the Yukon soon, as the territory’s power grid comes under strain from record-high energy demand.

This extended freeze is the result of a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. 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.

Pronounced Disparity with US Warmth

Conversely, sections of America recorded the hottest December 25th in their history 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 instead of the heart of winter.

A number of states broke historical records for December 25th warmth. The capital of Oklahoma soared to 25C on Christmas Day, surpassing the previous peak of 22C set in 1982. Cities including Austin and Dallas, in Texas, and Charlotte, North Carolina similarly saw thermometers rise past the 25C mark.

Heat-Dome Effect Drives the Heat

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with unseasonable heat forecast to sweep through the American Southeast soon.

The warmth has been fuelled by a strong upper-level ridge extending from the desert south-west towards the north and east, establishing a classic heat-dome pattern. Such a configuration results in a widespread high-pressure system over a large portion of North America, trapping warm air near the surface. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.