Chinook winds

Chinook winds /ʃɪˈnʊk/, or simply Chinooks, are föhn winds in the interior West of North America, where the Canadian Prairies and Great Plains meet various mountain ranges, although the original usage is in reference to wet, warm coastal winds in the Pacific Northwest.

Chinook is claimed by popular folk-etymology to mean ‘ice-eater’, but it is really the name of the people in the region where the usage was first derived. The reference to a wind or weather system, simply ‘a Chinook’, originally meant a warming wind from the ocean into the interior regions of the Pacific Northwest of the USA (the Chinook people lived near the ocean, along the lower Columbia River).

A strong föhn wind can make snow one foot (30 cm) deep almost vanish in one day. The snow partly melts and partly evaporates in the dry wind. Chinook winds have been observed to raise winter temperature, often from below −20 °C (−4 °F) to as high as 10–20 °C (50–68 °F) for a few hours or days, then temperatures plummet to their base levels. The greatest recorded temperature change in 24 hours was caused by Chinook winds on 15 January 1972, in Loma, Montana; the temperature rose from −48 to +9 °C (−54 to +49 °F).

Chinooks are most prevalent over southern Alberta in Canada, especially in a belt from Pincher Creek and Crowsnest Pass through Lethbridge, which get 30–35 Chinook days per year, on average. Chinooks become less frequent further south in the United States, and are not as common north of Red Deer, but they can and do occur annually as far north as High Level in northwestern Alberta and Fort St. John in northeastern British Columbia, and as far south as Albuquerque, New Mexico.

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