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Northern Canada has been gripped by a severe and lengthy Arctic outbreak, with temperatures hovering from 20 to 40 degrees below zero for multiple weeks. A reading of -55.7 Celsius was logged in Braeburn, Yukon, on Tuesday, marking its chilliest December reading since 1975.

Prolonged Freeze in the Deep Minus Forties

Similarly, the communities of Mayo and Dawson experienced over two straight weeks of nights colder than minus 40 degrees, with the temperature in Mayo bottoming out at -50.4 degrees Celsius on Monday. Whitehorse also recorded ten separate nights when temperatures dropped below -30C.

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

December 26th was anticipated to usher in readings no higher than -20 Celsius through a wide swath, from Edmonton in the west to Quebec in the east.

Likely to Linger For Days to Come

This harsh winter weather is expected to continue through the start of January. There are warnings of possible electrical grid strain in Yukon territory in the coming days, as the territory’s power grid comes under strain from historically high electricity consumption.

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 gradually, enabling milder Pacific air to move across America and reach into portions of southern Canada.

Dramatic Difference Compared to Stateside Temperatures

In stark contrast, parts of the US experienced historically high temperatures for Christmas as readings skyrocketed 15 to 30 degrees Celsius above normal. For numerous locations, the weather resembled a spring day in April or May rather than the end of December.

A number of states broke historical records for December 25th warmth. In Oklahoma, Oklahoma City hit 25C on Tuesday, 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.

High-Pressure System Fuels Warmth

Unseasonable heat is predicted to persist through Boxing Day and the days ahead, with unseasonable heat forecast to sweep into the south-eastern states later in the week.

The warmth has been fuelled by a robust atmospheric ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. This pattern establishes a broad area of high pressure blanketing a significant part of the landmass, which holds warm air close to the ground. As air sinks through the atmosphere, it compresses and heats further, allowing unusually warm temperatures to build.