The "snow eater" that can melt a foot of snow in a single day

Countries & Cities · Published 12 October 2026 · Updated 25 October 2026 Swipe more like this →

In short: In the North American interior, a sudden surge of warmth can transform a frozen landscape in hours. Known as Chinook winds, these powerful föhn winds can raise winter temperatures from below −20 °C to as high as 20 °C, causing snow to vanish through a rapid process of melting and sublimation.

Chinook winds are categorized into two distinct types. Coastal Chinooks are persistent, wet, southwesterly winds blowing from the ocean that sustain the temperate rainforests of the Pacific Northwest. In contrast, interior Chinooks are occasional, warm, and dry föhn winds that descend the eastern slopes of mountain ranges, such as the Rockies, affecting regions like the Canadian Prairies and the Great Plains.

The mechanism behind this sudden warmth is adiabatic heating. As moist air rises on the windward slopes, it cools at a moist adiabatic rate of approximately 5 °C per 1,000 meters. Once the air has lost its moisture as precipitation, it descends the leeward side, warming at a much faster dry adiabatic rate of 10 °C per 1,000 meters. This rapid compression makes the air significantly warmer and drier by the time it reaches the valley floors.

These winds are not without disruption. In southern Alberta, the phenomenon is prevalent, with areas like Pincher Creek and Crowsnest Pass experiencing an average of 30 to 35 Chinook days per year. While they can cause dramatic temperature spikes—such as a recorded rise of 25.5 °C in one hour in Pincher Creek on 6 January 1966—they also present challenges. For gardeners, the midwinter thaws can disrupt plant dormancy, making vegetation vulnerable to subsequent cold waves. In urban centers like Calgary, these winds can trap pollutants at street level, creating inversion smog.

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