Chinook winds, or simply Chinooks, are two types of prevailing warm, generally westerly winds 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, downslope wind that occurs in the leeward, lee (downwind side) of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped m ...

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 (sometimes Cascadia, or simply abbreviated as 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 ...

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 Temperate rainforests are coniferous or broadleaf forests that occur in the temperate zone and receive heavy rain. Temperate rain forests occur in oceanic moist regions around the world: the Pacific temperate rain forests of North American Paci ...

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 (french: Grandes Plaines), sometimes simply "the Plains", is a broad expanse of flatland in North America. It is located west of the Mississippi River and east of the Rocky Mountains, much of it covered in prairie, steppe, an ...

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 Bla ...

call these winds the "snow eater"; however, the more commonly used term "Chinook" originates from the name of the eponymous

Chinook people Chinookan peoples include several groups of Indigenous peoples of the Pacific Northwest Coast, Indigenous people of the Pacific Northwest in the United States who speak the Chinookan languages. Since at least 4000 BCE Chinookan peoples have res ...

, who lived near the ocean, along the lower

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

, 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 one foot (30 cm) 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 expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

, 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.

In the Pacific Northwest

"Chinook" is used for coastal Chinook winds in

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

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

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

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 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 gales 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 Classifications of snow describe and categorize the attributes of snow-generating weather events, including the individual crystals both in the air and on the ground, and the deposited snow pack as it changes over time. Snow can be classified ...

, sometimes to sea level. 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 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 and the Thompson River- Okanagan 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, and partly because of the additional number of precipitation-catching mountain ranges between

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

and

Calgary Calgary ( ) is the largest city in the western Canadian province of Alberta and the largest metro area of the three Prairie Provinces. As of 2021, the city proper had a population of 1,306,784 and a metropolitan population of 1,481,806, makin ...

. 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 , settlement_type = Region of British Columbia , image_skyline = , nickname = "The Coast" , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 = British ...

, and coastal Washington and Oregon, and in particular, the term is used in the Puget 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 ( ; Canadian ) are Indigenous peoples who inhabit Canada's three Prairie Provinces, as well as parts of British Columbia, the Northwest Territories, and the Northern United States. They have a shared history and culture which derives ...

employees of the Hudson's Bay Company, who were familiar with the Chinook people and country, brought the name east of the Cascades and Rockies, along with their own ethnified 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. While on the one hand this tale tells a tribal family-relations story, and family/tribal history as well, it also seems to be a parable of a typical weather pattern of a southwesterly wind at first bringing snow, then rain, and also of the melting of a glacier, namely the Place Glacier near

Gates Lake Gates Lake, also known as Birken Lake, Tenass Lake, Halfway Lake, and Summit Lake, is a small lake located at the summit of the Pemberton Portage area of the one-time Lakes Route through the Coast Mountains, located at the summit of a low pass co ...

at Birken. Thus, it also tells of a migration of people to the area – or a war, depending on how the details of the legend might be read, with Chinook-wind taking the part of

Helen Helen may refer to: People * Helen of Troy, in Greek mythology, the most beautiful woman in the world * Helen (actress) (born 1938), Indian actress * Helen (given name), a given name (including a list of people with the name) Places * Helen, ...

in a First Nations analogue to the Trojan War.

Chinooks in Alberta and eastern British Columbia

Interior Chinooks are most prevalent over southern

in Canada, especially in a belt from

Pincher Creek Pincher Creek is a town in southern Alberta, Canada. It is located immediately east of the Canadian Rockies, west of Lethbridge and south of Calgary. History For centuries before European settlers reached this area and inhabited it, Indigen ...

and Crowsnest Pass through

Lethbridge Lethbridge ( ) is a city in the province of Alberta, Canada. With a population of 101,482 in its 2019 Alberta municipal censuses, 2019 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, but they can and do occur annually as far north as

High Level High Level is a town in northern Alberta, Canada. It is located at the intersection of the Mackenzie Highway (Highway 35) and Highway 58, approximately north of Edmonton and south of Yellowknife, Northwest Territories. High Level is located w ...

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 southwestern Alberta, interior Chinook winds can gust in excess of hurricane force . On 19 November 1962, an especially powerful Chinook in Lethbridge gusted to . In Pincher Creek, the temperature rose by , from , in one hour on 6 January 1966. Trains have been known to be derailed by interior Chinook winds. 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.

, Alberta also gets many interior Chinooks – the Bow Valley in the

Canadian Rockies The Canadian Rockies (french: Rocheuses canadiennes) or Canadian Rocky Mountains, comprising both the Alberta Rockies and the British Columbian Rockies, is the Canadian segment of the North American Rocky Mountains. It is the easternmost part ...

west of the city acts as a natural wind tunnel, funneling the chinook winds. On 27 February 1992, Claresholm, Alberta, a small city just south of Calgary, recorded a temperature of ; again, the next day was recorded. These are some of Canada's highest February temperatures.

Clashing with Arctic air mass

The interior Chinooks can seem to battle with Arctic

air masses In meteorology, an air mass is a volume of air defined by its temperature and humidity. Air masses cover many hundreds or thousands of square miles, and adapt to the characteristics of the surface below them. They are classified according to la ...

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 A Föhn (Foehn) cloud is any cloud associated with a Föhn (Foehn), usually an Orographic lift, orographic cloud, a mountain wave cloud, or a lenticular cloud. Föhn is a regional term referring to winds in the Alps. See also * Cloud types * F� ...

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 that are formed by rising thermals. More specifically, the term ''stratus'' is used to describe flat, haz ...

s, caused by air rippling over the mountains due to

orographic lifting 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 Adiabatic cooling, adiabatically, which can raise the relative humid ...

. 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 southern New Zealand. 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). 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 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 that occurs in the leeward, lee (downwind side) of a mountain range. It is a rain shadow wind that results from the subsequent adiabatic warming of air that has dropped m ...

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

basswood ''Tilia americana'' is a species of tree in the family Malvaceae, native to eastern North America, from southeast Manitoba east to New Brunswick, southwest to northeast Oklahoma, southeast to South Carolina, and west along the Niobrara River to ...

, some apple,

raspberry The raspberry is the edible fruit of a multitude of plant species in the genus ''Rubus'' of the rose family, most of which are in the subgenus '' Idaeobatus''. The name also applies to these plants themselves. Raspberries are perennial with w ...

, and juneberry varieties, and

Amur maple ''Acer ginnala'', the Amur maple, is a plant species with woody stems native to northeastern Asia from easternmost Mongolia east to Korea and Japan, and north to the Russian Far East in the Amur River valley. It is a small maple with deciduous ...

s. 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 common neurological disorder characterized by recurrent headaches. Typically, the associated headache affects one side of the head, is pulsating in nature, may be moderate to severe in intensity, and could last from a few hou ...

headaches suffered by the locals. At least one study conducted by the department of clinical neurosciences at the University of Calgary supports that belief. They are popularly believed to increase irritability and

sleeplessness Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...

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

inversion Inversion or inversions may refer to: Arts * , a French gay magazine (1924/1925) * ''Inversion'' (artwork), a 2005 temporary sculpture in Houston, Texas * Inversion (music), a term with various meanings in music theory and musical set theory * ...

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 odor. 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. In 1983, on the 45th floor bout 145 m (460 ft) above the streetof the Petro-Canada Center, carpenters worked shirtless in +12 °C, windy conditions (temperature reported to them by overhead crane operator), but were chagrined to find out the street temperature was still −20 °C as they left work at 3:30 that afternoon.

Chinooks and föhn winds in the inland United States

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

s by meteorologists and climatologists are called 'Chinooks'. Regardless of the name, föhns can occur on the

leeward Windward () and leeward () are terms used to describe the direction of 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 of reference ...

side of any nearby mountain range. The föhns called 'Chinook winds' are seen throughout most of inland western North America, particularly the Rocky Mountain region. Montana 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 −54 °F to 49 °F (−48 °C to 9 °C), a 103 °F (58 °C) change in temperature. Spearfish, South Dakota holds the world record for the fastest increase in temperature. On January 22, 1943, the temperature increased from −4 °F to 45 °F (−20 °C to 7 °C), a 49 °F (27 °C) change in temperature. This occurred in just 2 minutes.Parker, Watson (1981). – ''Deadwood: The Golden Years''. – Lincoln, Nebraska: The University of Nebraska. – p.158. – . Rapid City, South Dakota holds the world record for the fastest decrease in temperature. On January 10, 1911, the temperature decreased from 60 °F to 13 °F (16 °C to −11 °C), a 47 °F (26.1 °C) 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, home to the

Squamish people The Squamish people (Squamish language, Squamish: ''Skwxwú7mesh'' , historically transliterated as Sko-ko-mish) are an Indigenous peoples of the Pacific Northwest Coast, indigenous people of the Pacific Northwest Coast. Archaeological evidence sh ...

, 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 wind ...

''. 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 (french: La chaîne Côtière) 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 Coast of British Columbia ...

towards the coast. A similar, local föhn wind regularly occurs in the Cook Inlet region in Alaska, as air moves over the Chugach Mountains between Prince William Sound and

Portage Glacier Portage Glacier is a glacier on the Kenai Peninsula of the U.S. state of Alaska and is included within the Chugach National Forest. It is located south of Portage Lake and 6 km (4 mi) west of Whittier. Portage Glacier was a local n ...

Anchorage Anchorage () is the largest city in the U.S. state of Alaska by population. With a population of 291,247 in 2020, it contains nearly 40% of the state's population. The Anchorage metropolitan area, which includes Anchorage and the neighboring Ma ...

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