Chinook winds, or simply Chinooks, are two types of prevailing warm, generally

westerly wind The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes (about 30 ...

s in western North America: Coastal Chinooks and interior Chinooks. The coastal Chinooks are persistent seasonal, wet, southwesterly winds blowing in from the ocean. The interior Chinooks are occasional warm, dry

föhn wind A Foehn, or Föhn (, , , ), is a type of dry, relatively warm katabatic wind, downslope wind in the leeward, lee of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of ...

s blowing down the eastern sides of interior mountain ranges. The coastal Chinooks were the original term, used along the northwest coast, and the term in the interior of North America is later and derives from the coastal term. * Along the

Pacific Northwest The Pacific Northwest (PNW; ) is a geographic region in Western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common ...

coast, where the name is pronounced ('chin'+'uk'), the name refers to wet, warm winds off the ocean from the southwest; this is the original use of the term. The coastal Chinook winds deliver tremendous amounts of moisture both as rain along the coast and snow in the coastal mountains, that sustain the characteristic temperate rainforests and climate of the

* In North American western interior, the same name is used for

s, generally, where the

Canadian Prairies The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...

and

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

lie immediately east of various interior mountain ranges. There the name is pronounced ('shin'+'uk'). The same warm, wet coastal winds can also become the warm

s on the eastern sides of mountain ranges, after having lost their moisture on the western sides; however, due to expanded use of the term in the interior for any

, interior Chinooks are not necessarily originally coastal Chinooks. In the interior of North America, the

Blackfoot people The Blackfoot Confederacy, ''Niitsitapi'', or ''Siksikaitsitapi'' (ᖹᐟᒧᐧᒣᑯ, meaning "the people" or " Blackfoot-speaking real people"), is a historic collective name for linguistically related groups that make up the Blackfoot or Bl ...

call these winds the "snow eater"; however, the more commonly used term "Chinook" originates from the name of the eponymous Chinook people, who lived near the ocean, along the lower

Columbia River The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river headwater ...

, where the term was first derived. The reference to "a Chinook" wind or weather system originally meant, to euro-American settlers along the Pacific Northwest coast, a warming wind from the ocean blowing into the interior regions of the

of the North America. A strong

can make snow deep almost vanish in one day. The snow partly sublimates and partly melts and evaporates in the dry wind. Chinook winds have been observed to raise winter

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

, often from below to as high as for a few hours or days, then temperatures plummet to their base levels. Its speed is generally between 16 km/h (10mph) and 60 km/h (37.5mph), gusting to 100 km/h (62.5 mph).

In the Pacific Northwest

"Chinook" is used for coastal Chinook winds in

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, and is the original use of the term, being rooted in the lore of coastal natives and immigrants, and brought to

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

by French-speaking fur-traders. Such winds are extremely wet and warm and arrive off the western coast of North America from the southwest. These same winds have more recently been called the pineapple express, since they are of tropical origin, roughly from the area of the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

near Hawaii. The air associated with a coastal Chinook is stable; this minimizes wind gusts and often keeps winds light in sheltered areas. In exposed areas, fresh

gale A gale is a strong wind; the word is typically used as a descriptor in nautical contexts. The U.S. National Weather Service defines a gale as sustained surface wind moving at a speed between .

s are frequent during a Chinook, but strong gale- or storm-force winds are uncommon; most of the region's stormy winds come when a fast "westerly" jet stream lets air masses from temperate and subarctic latitudes clash. When a coastal Chinook comes in when an Arctic air mass is holding steady over the coast, the tropical dampness brought in suddenly cools, penetrating the frozen air and coming down in volumes of powder snow, sometimes to

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

. Snowfalls and the cold spells that spawned them only last a few days during a Chinook; as the warm coastal Chinooks blow from the southwest, they push back east the cold Arctic air. The snow melts quickly and is gone within a week. The effects on the

Interior of British Columbia The British Columbia Interior, popularly referred to as the BC Interior or simply the Interior, is a geographic region of the Canadian province of British Columbia. While the exact boundaries are variously defined, the British Columbia Interior ...

when a coastal Chinook is in effect are the reverse. In a rainy spell, most of the heavy moisture will be wrung out of the rising air as a consequence of crossing over the mountain ramparts before the air mass descends (and hence warms and dries) into the

Fraser Canyon The Fraser Canyon is a major landform of the Fraser River where it descends rapidly through narrow rock gorges in the Coast Mountains en route from the Interior Plateau of British Columbia to the Fraser Valley. Colloquially, the term "Fraser Ca ...

and the

Thompson River The Thompson River is the largest tributary of the Fraser River, flowing through the south-central portion of British Columbia, Canada. The Thompson River has two main branches, the South Thompson River and the North Thompson River. The river ...

Okanagan The Okanagan ( ), also called the Okanagan Valley and sometimes the Okanagan Country, is a region in the Canadian province of British Columbia defined by the basin of Okanagan Lake and the Canadian portion of the Okanagan River. It is part of ...

area. The effects are similar to those of an Albertan interior Chinook, though not to the same extreme, partly because the Okanagan is relatively warmer than

the Prairies The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...

, and partly because of the additional number of precipitation-catching mountain ranges between

Kelowna Kelowna ( ) is a city on Okanagan Lake in the Okanagan, Okanagan Valley in the British Columbia Interior, southern interior of British Columbia, Canada. It serves as the head office of the Regional District of Central Okanagan. The name Kelowna ...

and

Calgary Calgary () is a major city in the Canadian province of Alberta. As of 2021, the city proper had a population of 1,306,784 and a metropolitan population of 1,481,806 making it the third-largest city and fifth-largest metropolitan area in C ...

. When the coastal Chinook brings snow to the coast during a period of coastal cold, bright but chilly weather in the interior will give way to a slushy melting of snow, more due to the warm spell than because of rain.

Pronunciation in the Pacific Northwest

The word "Chinook" remains in common use among local fishermen and people in communities along the

British Columbia Coast The British Columbia Coast, popularly referred to as the BC Coast or simply the Coast, is a geographic region of the Provinces and territories of Canada, Canadian province of British Columbia. As the entire western continental coastline of Canada ...

, and coastal Washington and

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

, and in particular, the term is used in the

Puget Sound Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...

area of Washington. Coastal "Chinook" is not pronounced ''shin-uk'' () as it is in the interior, east of the Cascades, but is in the original coastal pronunciation ''chin-uk'' (). In

and other parts of the

, the word Chinook was predominantly pronounced . However, the common pronunciation current throughout most of the inland

, Alberta, and the rest of Canada, is , as in French. This difference may be because it was the

Métis The Métis ( , , , ) are a mixed-race Indigenous people whose historical homelands include Canada's three Prairie Provinces extending into parts of Ontario, British Columbia, the Northwest Territories and the northwest United States. They ha ...

employees of the

Hudson's Bay Company The Hudson's Bay Company (HBC), originally the Governor and Company of Adventurers of England Trading Into Hudson’s Bay, is a Canadian holding company of department stores, and the oldest corporation in North America. It was the owner of the ...

, who were familiar with the Chinook people and country, brought the name east of the Cascades and Rockies, along with their own ethnic pronunciation. Early records are clear that ''tshinook'' was the original pronunciation, before the word's transmission east of the Rockies.

First nations myth from British Columbia

Native legend of the Lil'wat subgroup of the St'at'imc tells of a girl named Chinook-Wind, who married Chinook Glacier, and moved to his country, which was in the area of today's Birkenhead River. She pined for her warm sea-home in the southwest, and sent a message to her people. They came to her in a vision in the form of snowflakes, and told her they were coming to get her. They came in great number and quarrelled with Glacier over her, but they overwhelmed him and in the end she went home with them.

Chinooks in Alberta and eastern British Columbia

Interior Chinooks are most prevalent over southern

in Canada, especially in a belt from Pincher Creek and

Crowsnest Pass Crowsnest Pass (sometimes referred to as Crow's Nest Pass, ) is a low mountain pass across the Continental Divide of the Canadian Rockies on the Alberta–British Columbia border. Geography The pass is located in southeast British Columbia an ...

through

Lethbridge Lethbridge ( ) is a city in the province of Alberta, Canada. With a population of 106,550 in the 2023 Alberta municipal censuses, 2023 municipal census, Lethbridge became the fourth Alberta city to surpass 100,000 people. The nearby Canadian ...

, which get 30–35 Chinook days per year, on average. Interior Chinooks become less frequent further south in the United States, and are not as common north of

Red Deer The red deer (''Cervus elaphus'') is one of the largest deer species. A male red deer is called a stag or Hart (deer), hart, and a female is called a doe or hind. The red deer inhabits most of Europe, the Caucasus Mountains region, Anatolia, Ir ...

, but they can and do occur annually as far north as High Level in northwestern Alberta and Fort St. John in northeastern

, and as far south as Las Vegas, Nevada, and occasionally to Carlsbad, in eastern New Mexico. In Pincher Creek, the temperature rose by , from , in one hour on 6 January 1966. During the winter, driving can be treacherous, as the wind blows snow across roadways, sometimes causing roads to vanish and snowdrifts to pile up higher than a metre. Empty semitrailer trucks driving along Highway 3 and other routes in southern Alberta have been blown over by the high gusts of wind caused by interior Chinooks. On 27 February 1992,

Claresholm Claresholm is a town located within southern Alberta, Canada. It is located on Highway 2, approximately northwest of the City of Lethbridge and south of the City of Calgary. History The location was originally a watering stop for steam engin ...

, Alberta, a town just south of Calgary, recorded a temperature of ; again, the next day was recorded.

Clashing with Arctic air mass

The interior Chinooks can seem to battle with Arctic air masses at times. This clash of temperatures can remain stationary, or move back and forth, in the latter case causing such fluctuations as a warm morning, a bitterly cold afternoon, and a warm evening. A curtain of fog often accompanies the clash between warm to the west and cold to the east.

Chinook arch

Two common cloud patterns seen in the interior during this time are a chinook arch overhead, and a bank of clouds (also referred to as a cloud wall) obscuring the mountains to the west. The bank appears to be an approaching storm, but does not advance any further to the east. One of its most striking features of the interior Chinook weather system is the ''Chinook arch'', a föhn cloud in the form of a band of stationary

stratus cloud Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds formed by rising thermals. The term ''stratus'' describes flat, hazy, featureless clouds at low altit ...

s, caused by air rippling over the mountains due to orographic lifting. To those unfamiliar with it, the Chinook arch may at times look like a threatening storm cloud, however, the arch clouds rarely produce rain or snow. They can also create stunning sunrises and sunsets. A similar phenomenon, the nor'west arch, also a föhn cloud, is seen in eastern

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. The stunning colors seen in the Chinook arch are quite common. Typically, the colours will change throughout the day, starting with yellow, orange, red, and pink shades in the morning as the sun comes up, grey shades at midday changing to pink / red colours, and then orange / yellow hues just before the sun sets. Image:Chinook-arch.JPG, Chinook arch over Calgary, 6 January 2003 Image:chinook-arch-01.jpg, The extreme colors of a Chinook arch File:Chinook19.11.05.jpg, Chinook arch in Calgary, Alberta, 19 November 2005 Image:Chinook Arch-Calgary.JPG, Chinook arch over Calgary, March 2007 Image:Okanagan-Arch.jpg, Chinook arch over Kelowna, BC, Canada, 2 October 2007

Cause of occurrence

The interior Chinook is a

, a rain shadow wind which results from the subsequent adiabatic warming of air which has dropped most of its moisture on windward slopes (

orographic lift Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and cr ...

). As a consequence of the different adiabatic rates of moist and dry air, the air on the leeward slopes becomes warmer than equivalent elevations on the windward slopes. Sometimes the interior Chinooks are caused by the same air flow as the coastal Chinooks: As moist winds from the Pacific (coastal Chinooks) are forced to rise over the mountains, the moisture in the air is condensed and falls out as precipitation, while the air cools at the moist adiabatic rate of The dried air then descends on the leeward side of the mountains, warming at the dry adiabatic rate of The turbulence of the high winds also can prevent the usual nocturnal

temperature inversion In meteorology, an inversion (or temperature inversion) is a phenomenon in which a layer of warmer air overlies cooler air. Normally, air temperature gradually decreases as altitude increases, but this relationship is reversed in an inver ...

from forming on the lee side of the slope, allowing night-time temperatures to remain elevated. Quite often, when the

coast is being drenched by rain, the windward (western) side of the Rockies is being hammered by snow (robbing the air of its moisture), and the leeward (eastern) side of the Rockies in Alberta is basking in a

föhn A Foehn, or Föhn (, , , ), is a type of dry, relatively warm downslope wind in the lee of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped most of its moisture on windw ...

Chinook. The three different weather conditions are all caused by the same flow of air, hence the confusion over the use of the name "Chinook wind".

Interior Chinooks and gardening on Great Plains

The frequent midwinter thaws by interior Chinooks in Great Plains country are more of a bane than a blessing to gardeners. Plants can be visibly brought out of dormancy by persistent, warm interior Chinook winds, or have their hardiness reduced even if they appear to remain dormant. In either case, they become vulnerable to later cold waves. Many plants which do well at

Winnipeg Winnipeg () is the capital and largest city of the Provinces and territories of Canada, Canadian province of Manitoba. It is centred on the confluence of the Red River of the North, Red and Assiniboine River, Assiniboine rivers. , Winnipeg h ...

– where constant cold maintains dormancy throughout the winter – are difficult to grow in the Alberta Chinook belt. Examples include basswood, some

apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...

raspberry The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...

, and juneberry varieties, and Amur maples. Native trees in the interior Chinook-affected areas of Alberta are known to be small, with much less growth than the same species growing in areas not affected by interior Chinook winds. This is once again caused by the "off-and-on" dormancy throughout winter.

Health

Interior Chinook winds are said to sometimes cause a sharp increase in the number of

migraine Migraine (, ) is a complex neurological disorder characterized by episodes of moderate-to-severe headache, most often unilateral and generally associated with nausea, and light and sound sensitivity. Other characterizing symptoms may includ ...

headaches suffered by the locals. At least one study conducted by the department of clinical neurosciences at the

University of Calgary {{Infobox university , name = University of Calgary , image = University of Calgary coat of arms without motto scroll.svg , image_size = 150px , caption = Coat of arms , former ...

supports that belief. They are popularly believed to increase

irritability Irritability is the excitatory ability that living organisms have to respond to changes in their environment. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimul ...

and sleeplessness. In mid-winter over major centres such as Calgary, interior Chinooks can often override cold air in the city,

trapping Animal trapping, or simply trapping or ginning, is the use of a device to remotely catch and often kill an animal. Animals may be trapped for a variety of purposes, including for meat, fur trade, fur/feathers, sport hunting, pest control, and w ...

the pollutants in the cold air and causing inversion

smog Smog, or smoke fog, is a type of intense air pollution. The word "smog" was coined in the early 20th century, and is a portmanteau of the words ''smoke'' and ''fog'' to refer to smoky fog due to its opacity, and odour. The word was then inte ...

. At such times, it is possible for it to be cold at street level and much warmer at the tops of the skyscrapers and in higher terrain.

Chinooks and föhn winds in the inland United States

In the North American western interior, winds that are generally called

s by

meteorologist A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmosphere of Earth, atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists ...

s and

climatologist Climatology (from Greek , ''klima'', "slope"; and , ''-logia'') or climate science is the scientific study of Earth's climate, typically defined as weather conditions averaged over a period of at least 30 years. Climate concerns the atmospheric ...

s are called "Chinooks". Regardless of the name, föhns can occur on the

leeward In geography and seamanship, windward () and leeward () are directions relative to the wind. Windward is ''upwind'' from the point of reference, i.e., towards the direction from which the wind is coming; leeward is ''downwind'' from the point o ...

side of any nearby mountain range. The föhns called "Chinook winds" are seen throughout most of inland western North America, particularly the

Rocky Mountain The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of Western Canada, to New Mexico in ...

region.

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

especially has a significant amount of föhn winds throughout much of the state during the winter months, but particularly coming off the Rocky Mountain Front in the northern and west-central areas of the state. On rare occasions, Chinook winds generated on the eastern slope of the Rocky Mountains have reached as far east as Wisconsin.

Records

Loma, Montana has the world record for the most extreme temperature change in a 24-hour period. On January 15, 1972, the temperature increased from , a change in temperature. Spearfish, South Dakota holds the world record for the fastest increase in temperature. On January 22, 1943, the temperature increased from , a change in temperature. This occurred in just 2 minutes.Parker, Watson (1981). – ''Deadwood: The Golden Years''. – Lincoln, Nebraska: The University of Nebraska. – p.158. – . Spearfish, South Dakota also holds the world record for the fastest decrease in temperature, for the same day. On January 22, 1943, the temperature decreased from , a change in temperature. This occurred in 27 minutes.

Rapid City, South Dakota Rapid City is the county seat of Pennington County, South Dakota, United States. It is located on the eastern slope of the Black Hills in western South Dakota and was named after Rapid Creek (South Dakota), Rapid Creek, where the settlement deve ...

had the world record for the fastest decrease in temperature. On January 10, 1911, the temperature decreased from , a change in temperature.

Squamish winds, williwaws, and Chugach föhns

The resulting outflow wind is more or less the opposite of

coastal Chinook. These are called a squamish in certain areas, rooted in the direction of such winds coming down out of

Howe Sound Howe Sound (, ) is a roughly triangular sound (geography), sound, that joins a network of fjords situated immediately northwest of Vancouver, British Columbia, Canada. It was designated as a UNESCO Biosphere Reserve in 2021. Geography Howe Sound ...

, home to the

Squamish people The Squamish people ( , historically transliterated as Sko-ko-mish) are an indigenous peoples of the Pacific Northwest Coast, indigenous people of the Pacific Northwest Coast. Archaeological evidence shows they have lived in the area for more th ...

, and in Alaska are called a ''

williwaw In meteorology, a williwaw (archaic spelling williwau) is a sudden blast of wind descending from a mountainous coast to the sea. The word is of unknown origin, but was earliest used by British seamen in the 19th century. The usage appears for win ...

''. They consist of cold airstreams from the continental air mass pouring out of the interior plateau via certain river valleys and canyons penetrating the

Coast Mountains The Coast Mountains () are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the British Columbia Coast, Coast of British Columbia sout ...

towards the coast. A similar, local föhn wind regularly occurs in the

Cook Inlet Cook Inlet (; Sugpiaq language, Sugpiaq: ''Cungaaciq'') stretches from the Gulf of Alaska to Anchorage, Alaska, Anchorage in south-central Alaska. Cook Inlet branches into the Knik Arm and Turnagain Arm at its northern end, almost surrounding ...

region in Alaska, as air moves over the

Chugach Mountains The Chugach Mountains of southern Alaska are the northernmost of the several mountain ranges that make up the Pacific Coast Ranges of the western edge of North America. The range is about long and wide, and extends from the Knik and Turnag ...

between

Prince William Sound Prince William Sound ( Sugpiaq: ''Suungaaciq'') is a sound off the Gulf of Alaska on the south coast of the U.S. state of Alaska. It is located on the east side of the Kenai Peninsula. Its largest port is Valdez, at the southern terminus of the ...

and Portage Glacier.

Anchorage Anchorage, officially the Municipality of Anchorage, is the most populous city in the U.S. state of Alaska. With a population of 291,247 at the 2020 census, it contains nearly 40 percent of the state's population. The Anchorage metropolita ...

residents often believe the warm winds which melt snow and leave their streets slushy and muddy are a midwinter gift from Hawaii, following a common mistake that the warm winds come from the same place as the similar winds near the coasts in southern British Columbia, Washington, and Oregon.

References

{{DEFAULTSORT:Chinook Wind Climate of the Rocky Mountains Winds Natural history of Alberta Western United States Climate of Canada Föhn effect ml:കാറ്റ്#ചിനൂക്ക്