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A prolonged deep freeze has enveloped an intense and prolonged cold spell, with readings persisting from 20 to 40 degrees below zero for weeks. This week, the Yukon community of Braeburn saw the mercury drop to -55.7C, its coldest December temperature in half a century.

Prolonged Freeze Below -40C

Meanwhile, Mayo and Dawson endured over two straight weeks of nights dipping under the minus 40 Celsius threshold, with the temperature in Mayo bottoming out at -50.4 degrees Celsius at the start of the week. Whitehorse also recorded 10 nights when the cold dipped under -30 Celsius.

The bitter chill extended its reach south during the holiday season. In Edmonton, the Christmas overnight low dipped under -28 degrees Celsius.

December 26th was anticipated to usher in readings no higher than -20 Celsius across many regions, encompassing cities from Edmonton to Quebec.

Likely to Linger For Days to Come

The severe cold is forecast to persist through the start of January. Authorities have cautioned about potential power failures in the Yukon soon, as the system endures record-high pressure from historically high electricity consumption.

This extended freeze is the result of the Arctic vortex settling across the northern part of the continent this month, which funnels frigid northern air southward. 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.

Stark Contrast to American Heat

In stark contrast, parts of the US experienced their warmest Christmas Day on record as readings skyrocketed 15 to 30 degrees Celsius above normal. In many areas, conditions felt more typical of April or May rather than the end of December.

Multiple states established new Christmas temperature highs. In Oklahoma, Oklahoma City hit 25C on Tuesday, surpassing the previous peak of 22C set in 1982. Metropolitan areas such as Austin, Dallas, and Charlotte were also among those that recorded temperatures above 25C.

High-Pressure System Drives the Heat

Above-average warmth is expected to continue on December 26th and into the weekend, with unseasonable heat forecast to sweep across the southeastern US in the coming days.

The unseasonable temperatures are powered by a powerful high-altitude ridge stretching from the southwestern deserts northward and eastward, which generates a heat-dome phenomenon. This setup creates an extensive zone of high atmospheric pressure across much of the continent, effectively capping warm air at lower altitudes. Descending air compresses and adiabatically warms, allowing unusually warm temperatures to build.