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A prolonged deep freeze has enveloped a severe and lengthy Arctic outbreak, 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, marking its chilliest December reading in half a century.

Consecutive Nights Below -40C

In addition, the locales of Mayo and Dawson suffered through sixteen nights in a row below -40C, with Mayo experiencing a low of -50.4C at the start of the week. Whitehorse also recorded ten separate nights when the cold dipped under -30 Celsius.

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 readings no higher than -20 Celsius in numerous areas, from Edmonton in the west to Quebec in the east.

Forecast to Persist into the New Year

The frigid conditions are predicted to linger into the new year. Authorities have cautioned about potential power failures in the Yukon soon, as its energy infrastructure faces unprecedented demand from peak power usage levels.

The prolonged chill has been caused by a stationary polar vortex above Canadian territory through December, enabling a surge of icy Arctic winds to descend. Next week, the cold air mass is expected to retreat north slowly, permitting warmer Pacific winds to flow over America and reach into portions of southern Canada.

Stark Contrast with US Warmth

In stark contrast, parts of the US experienced historically high temperatures for Christmas 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. Oklahoma City, Oklahoma, reached 25 degrees Celsius on Christmas, surpassing the previous peak of 22C set in 1982. Urban centers like Austin, Dallas, and Charlotte, North Carolina also logged readings above 25 degrees Celsius.

Heat-Dome Effect Drives the Heat

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with atypical high temperatures expected to spread through the American Southeast soon.

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, trapping warm air near the surface. Descending air compresses and adiabatically warms, fostering the buildup of exceptional warmth.