2021 Western North America heat wave

The 2021 Western North America heat wave was an extreme heat wave that affected much of Western North America from late June through mid-July 2021. Rapid attribution analysis found this was a 1000-year weather event, made 150 times more likely by climate change. The heat wave affected Northern California, Idaho, Western Nevada, Oregon, and Washington in the United States, as well as British Columbia, and in its latter phase, Alberta, Manitoba, the Northwest Territories, Saskatchewan, and Yukon, all in Canada. It also affected inland regions of Central and Southern California, Northwestern and Southern Nevada and parts of Montana, though the temperature anomalies were not as extreme as in the regions farther north.

The heat wave appeared due to an exceptionally strong ridge centered over the area, whose strength was linked to the effects of climate change. It resulted in some of the highest temperatures ever recorded in the region, including the highest temperature ever measured in Canada at 49.6 °C (121.3 °F), as well as the highest temperatures in British Columbia, in the Northwest Territories, in the state of Washington as well as a tied record in Oregon. The record-high temperatures associated with the heat wave stretched from Oregon to northern Manitoba, and daily highs were set as far east as Labrador and as far southwest as Southern California. However, the Pacific Northwest suffered the vast majority of the disruption and damage connected with the extreme weather event.

The heat wave sparked numerous extensive wildfires, some reaching hundreds of square kilometers in area, which led to widespread disruption on the roads. One of them destroyed the village of Lytton, British Columbia, the day after it had set a record high temperature for Canada. The heat also damaged the road and rail infrastructure, forced closures of businesses, disrupted cultural events, and melted snowcaps, in some cases resulting in flooding. The heat wave also caused extensive damage to crops across the region, which was seen as likely to result in higher food prices globally, though the losses have yet to be calculated. The National Oceanic and Atmospheric Administration (NOAA) estimated that the heatwave caused at least $8.9 billion (2021 USD) in damages in the USA.

The death toll exceeded 1,400 people, with a death toll of at least 808 estimated in western Canada. On July 6, the British Columbia Coroner Service released preliminary statistics that indicated 610 more sudden deaths than usual occurred in the province. Alberta logged 66 excess deaths the week of the heat wave. The Chief Coroner of British Columbia later said that in the week between June 25 to July 1, 569 deaths were confirmed to have had heat-related causes, and in a report released June 2022, the number was updated to 619. Confirmed deaths in the United States include at least 116 in Oregon (of which 72 are in Multnomah County, which includes Portland), and at least 112 in Washington and one death in Idaho; An analysis by '' The New York Times'' suggests that around 600 excess deaths occurred the week the heat wave passed through Washington and Oregon.

Meteorological history

On June 23, the United States National Weather Service warned of an approaching heat wave in the Pacific Northwest, whose origins could be traced to torrential rains in China. There, the warm, moist air rose and was eventually entrained by the jet stream, which transported it east over cooler waters. When that air current encountered an upper-level high-pressure zone, also called a ridge, it started to significantly deform on June 25, forcing to accommodate the high-pressure area south of the jet stream's meander. At the same time, the Southwestern states were enduring an intense drought, which had earlier allowed higher-than-average temperatures over the Southwestern United States, leading to a similar hot wave earlier in June. Its remnants then moved north to the Pacific Northwest. Six days later, Environment Canada issued a heat warning for Alberta, Saskatchewan, British Columbia, Manitoba, Yukon, and Northwest Territories.

These conditions made way for a massive Rex block, which is more often formed during La Niña years. In this situation, a high-pressure area stays in place for a long time and does not let cyclones pass through it, which could have cooled the region; in this particular case, the high-pressure area was sandwiched between two stationary lows, which prevented the high-pressure region from moving anywhere. As the Pacific Northwest, just as the Southwest, experienced severe drought conditions, the already warm air was heating more quickly than usual, which intensified the ridge so strongly it caused a heat dome. Indeed, on June 27, the height at which 500  hPa air pressure was sustained (geopotential height) was reported at in Prince George, British Columbiathe highest ever recorded in the area; adjacent stations have similarly reported record-high values. The downslope winds from the Cascades and other mountain ranges further warmed the air in the valleys.

After the heat dome hovered over British Columbia and the Northwestern United States for a few days, it began to move eastward, breaking records east of the Rocky Mountains, particularly in the northern parts of the Prairie provinces, but bringing relief to the Pacific coast. At this stage, the heat was kept between the warm and cold fronts of the low-pressure area that formed over southern Northwest Territories and was transported eastward towards Hudson Bay. Sweltering conditions were observed as far east as Montana, Manitoba, and Northwest Ontario, though the temperatures were not as high.

By July 4–5, the remnants of the heat dome crossed Hudson Bay and, weakened somewhat by the cool waters, entered Quebec, and after that, Labrador, briefly triggering temperatures of around . Having beaten daily records in some localities in the easternmost province of Canada, the high-pressure area entered the Atlantic Ocean on July 7, when the heat carried by the high-pressure system finally dissipated.

Climate change and additional factors

Climate change in Canada and in the United States are widely considered to have worsened the heat wave's unprecedented intensity and duration. According to a preliminary study, which has not yet been peer-reviewed, the heat wave would have been highly unlikely in the absence of anthropogenic climate change, the latter increasing the likelihood of such a heat wave at least 150-fold. According to this study, either the climate change made the heat wave more likely by increasing base temperatures and a combination of rare events, such as the recent drought and/or changes in the jet stream, resulted in the heat wave, or even a relatively small increase in mean global temperatures caused by climate change can pass a threshold that triggers a sharp increase in the probability of extreme heat wave phenomena.

While it is yet unknown whether the frequency of these omega blocks is due to global heating, according to the data provided by Verisk, the Pacific Northwest is among the fastest-heating regions in the continental United States and southern Canada. Moreover, the urban heat island effect could have further exacerbated the impact in cities. Based on historic data, several meteorologists noted that this phenomenon should be expected to occur only once over a thousand or several thousand years, and David Sauchyn, a scientist at the University of Regina, said that climate models had been predicting the heat wave of a similar intensity to happen in late 2020s at the earliest.

Temperature records

Much of the Pacific Northwest, normally known for its temperate weather in June, received maximum temperatures above normal during this heat wave. In fact, the temperatures were so anomalous that nighttime lows were higher than the average high temperatures that this region would normally observe at this time of year. Ground temperatures were also reaching extremes - in Wenatchee, Washington, it reached .

This heat wave, combined with other extreme weather occurrences elsewhere, yielded the hottest June on record in North America. It also contributed to the hottest June ever for some localities such as Victoria, Abbotsford, Kamloops and Edmonton, and in Portland, Oregon, as well as one of the hottest June mean temperatures for Seattle and Spokane. On a statewide level, June 2021 was the warmest on record in California, Nevada, Arizona, Utah and Idaho, and second warmest for Washington, Oregon and Montana, at least partly attributable to this heat wave.

Canada

The highest temperatures of the heat wave were registered in British Columbia, but areas as far east as Ontario were affected by the event. 103 all-time heat records were set across Western Canada.

British Columbia

The heat wave peaked in British Columbia on June 28–29. Most records of the coastal areas were made on June 28, while in the British Columbia Interior, the highest values were largely set the following day.

On June 28, records were set in Squamish, British Columbia at , Abbotsford at , Port Alberni at and Victoria at . Also, on the morning of June 28, a meteorological station at Simon Fraser University in Burnaby registered an overnight low of , the highest ever recorded in the province.

On June 27, local records were also set in Cultus Lake, Lillooet, Ashcroft () and Kamloops (). In all, there were 59 weather stations in B.C. that set records for hottest temperatures recorded for June 27. These were largely beaten in the following days (Kamloops, for instance, registered on June 28 and on June 29, the peak temperature recorded in a major population center in the region).

On June 29, the temperature in Lytton, British Columbia, hit , the highest temperature ever recorded in Canada, although a nearby more modern station reported that the extreme was 1 °C lower. The stations were temporarily isolated by the Lytton wildfire the next day. The record occurred after consecutively setting new record highs of on June 27 and on June 28. It is also the highest temperature ever recorded north of 45°N, the highest temperature in the U.S. or Canada recorded outside the Desert Southwest, and higher than the absolute maximum temperatures of Europe or South America.

Alberta

In Alberta, the highest heat was observed in the period from June 29 to July 1. Banff , Beaverlodge , Cochrane , Fort McMurray , Jasper , Grande Prairie , Hendrickson Creek , Nordegg , Red Earth Creek all saw the strongest heat ever measured in these communities, most after breaking all-time records of the previous day.

Calgary noted on June 29 and July 1, which stopped just 0.2 °C short of the highest observed temperature ever and beating the all-time records for June and July. Edmonton also saw temperatures approach the absolute maxima - the city centre registered on June 30, while the Edmonton International Airport, near Leduc, hovered around from June 29 to July 1. The heat wave had largely moved east by July 2, though e.g. Fort McMurray measured its fourth daily record in a row on that date.

Territories

In the Northwest Territories, on June 28, Nahanni Butte set a regional record at . Two days later, Fort Smith, just north of the Alberta border, reached , which beat the previous all-time territorial record, registered in the same place in 1941. It was also the new highest reliably recorded temperature above 60 degrees latitude.

Yukon was largely bypassed by the heat wave, but on June 28, some areas in the territory went over , including Whitehorse () and Teslin (), both of which were daily records. Teslin also beat the record for June 29, at .

Saskatchewan

Saskatchewan's heat records were mainly concentrated in the northern parts of the province. Stony Rapids saw the mercury reach on June 30, an all-time high and record temperatures were also set at Key Lake Airport, sometimes dubbed "the cold pole of Saskatchewan", and Collins Bay Airport on July 1, both at , as well as in Uranium City (). July highs were also observed in these settlements on the first day of the month, when 26 daily records were set across the province, most in northern communities.

Elsewhere, the heat arrived slightly later. Saskatoon reached on July 1 and beat the monthly record the following day, at , a tenth of degree below the all-time record. La Ronge registered an all-time high with a reading of . Regina, like most of the southern part of the province was spared the extremes reached in the northern parts, with a maximum of on July 2. The heat wave over Saskatchewan largely dissipated by July 3 and moved east.

Manitoba

In a similar way to Saskatchewan, the majority of heat records (including all-time highs) were noted in the northern parts of the province. A remote community of Tadoule Lake observed , beating the previous all-time record by , so did Lynn Lake (), while Churchill, on the shore of Hudson Bay, registered , the highest temperature for July.

Other parts of the province did not see heat as extreme as elsewhere, though 25 daily records were set on July 3, including in Winnipeg.

Ontario

Northwestern Ontario did not see all-time high records beaten, but several daily records were pushed higher: on July 3, Thunder Bay equalled , Geraldton saw , while the hottest temperature was in Pickle Lake, at .

Newfoundland and Labrador

Weakened by interaction with the Hudson Bay waters, and having not set any record in Quebec, the heat wave arrived to the mainland part of Newfoundland and Labrador, but before dissipating in the Atlantic Ocean, it still managed to beat some daily records. Hopedale registered on July 5, while Happy Valley-Goose Bay reached the following day.

United States

The heat wave broke numerous records by large margins. Several large cities, including Portland, Seattle, and Spokane, experienced high temperatures far exceeding and low temperatures higher than the area's normal daily high temperatures. The heat wave beat Washington's all-time heat record in Hanford () and tied one for Oregon ( at two places, including at Pelton Dam). The same temperature was noted in Peshastin in Chelan County, Washington, where temperatures soared to on June 29, slightly surpassing the previous all-time high for the state.

Oregon

On June 26, Portland broke its previous all-time record high temperature of , set in July 1965 and August 1981, with a temperature of . It topped that record again on June 27, with a temperature of . The following day, the temperature increased further to . These extremes also beat the previous record June temperature, set on June 26, 2006.

Salem, Oregon, reached on June 26, its record high temperature for June. It then hit degrees on June 27, breaking the record for the highest temperature ever recorded in that city, which was previously . Salem then exceeded the previous day's record temperature on June 28, with a maximum temperature of . However, not all the regions of the mid- Willamette Valley experienced extreme heat on June 28. Regions south of Salem, for example, did not see highs above mid-90s Fahrenheit on that day, likely due to cooler ocean air in the area.

The Willamette Valley also experienced extreme overnight temperature drops (twice the size of normal fluctuations) due to cooler air coming from the oceanPortland cooled a record during the night, while Salem almost approached its all-time largest temperature swing, from to .

Washington

Between 1894, when the records in Seattle began, and June 2021, temperatures over were only noted three times; however, the Seattle-Tacoma International Airport recorded three consecutive days of temperatures over . Notably, they rose to on June 27, only to be beaten to the following day. All of these values broke the previous June record (, 2017) by a large margin. The suburbs farther from the coast were even hottera local radio station in Maple Valley reported temperatures of .

On June 26, Port Angeles recorded an all-time record high of . The Quillayute Airport weather station, also on the Olympic Peninsula, reported on June 28, exceeding its prior record by .

On Mount Rainier, normally freezing temperatures reached degrees above on June 27. The heat wave was blamed for greater glacier melt on Mt. Rainier than had been seen in the state in the past 100 years.

East of the Cascades, cities such as Spokane and a few other cities measured record-breaking or -tying temperatures, beating several records over the period of a few days. On June 29, Spokane, Ephrata and Omak all reached their all-time records, at , and , respectively. These are the hottest temperatures measured since records began for those areas. Extremely warm minimum temperatures were also noted: Ephrata's thermometers did not go lower than on June 28 and on June 29, and all-time highest low temperature records were set at Spokane International Airport on June 29 () and June 30 (), during overnight hours.

It was even hotter on and near the Oregon-Washington border. In The Dalles, Oregon and Dallesport, on either side of the Columbia River, daytime high temperatures reached , tying the then all-time record for the state of Washington and beating the June statewide record by 5 degrees Fahrenheit. The same heat was measured in Tri-Cities on June 28–29. The state's new official temperature record was set at on June 29 in Hanford. The heat wave resulted in 128 all-time high temperature records set for individual weather stations across the state, including in Seattle.

California

Temperature records were observed in the northern part of the state. South Lake Tahoe observed on June 28, beating the previous June record, and tied or beaten daily records for three days in a row. In Redding, the temperatures soared to on June 27, a daily record, while in Siskiyou County, Montague tied an all-time high for the county, at .

Southern California was also impacted. Palm Springs registered on June 27, surpassing the previous daily record, while other communities, such as Palmdale, Campo and Idyllwild, tied with them.

Idaho

Being largely on the margin of the high pressure dome, Idaho did not see temperatures as extreme as elsewhere. In Lewiston, on the border with Washington, was noted on June 29, beating an all-time June record and becoming the third-highest temperature in the history of recordings for the city. Other localities in the Treasure Valley to the east were expected to sustain triple-digit heat for a week (which is in and of itself unusual) and in general to tie or beat daily records. Boise, for example, tied one for June 29 () and for June 30 (), and also recorded nine consecutive days of temperatures exceeding , which tied the record for such a streak. Records were also beaten in the Idaho Panhandle, with Coeur d'Alene registering , which surpassed the previous highest temperature for June and equaled the all-time high for the city.

Montana

Most of Montana was placed on heat advisories, but the areas that were most affected by the heat wave were on the extreme northwest and eastern parts of the state. Kalispell and Missoula registered temperatures of on June 29, both daily records and 1 °F short of the record for June; Libby succeeded in doing so, setting the plank at . In the eastern parts of the state, several daily records were also noted: Livingston reached on June 30 and Miles City saw two days later; Billings tied its daily record on July 1 and had not fallen below on July 3, while Glasgow bettered its July 1 record to , tied the daily high record the next day, and set the highest minimum temperatures on these days ( on July 2).

Deaths and injuries

Canada

The heat wave was the deadliest weather event in Canadian history.

Over 1,000 deaths occurred due to the direct consequences of the heat wave (such as hyperthermia). Most of the deaths occurred in Canada – about 600 more deaths than usual were noted in British Columbia and 66 in Alberta. It still unknown whether any of the excess deaths in Alberta were related to the heat wave, but the Chief Coroner of British Columbia stated that 569 casualties could be attributed to heat. A later report put the heat-related death toll at 619. She also said that in the prior five years, only three heat-related casualties had been registered. Among the deaths reported to the provincial coroner, Fraser and Vancouver Coastal health authorities saw several times more deaths than usual, and the Vancouver Island and Interior Health health districts noted double the expected number of dead during the week from June 25 to July 1. Most of the deaths were registered on June 29.

In British Columbia, E-Comm emergency dispatchers answered nearly 15,300 calls on June 26-27, which was about above normal for the month, and also deployed the ambulances 1,850 times on June 27 and 1,975 the following day - the highest number ever recorded for the province. Delays for non-emergency calls reached up to 16 hours in extreme cases. In addition to that, some ambulances were left inoperable as the emergency service was understaffed. These setbacks led to hours-long delays. The handling of the crisis drew criticism from the paramedics unions, which forced Adrian Dix, the provincial healthcare minister, to change the leader of British Columbia's emergencies response management to Jim Chu, former Vancouver's police chief, and to appoint a chief ambulance officer.

United States

In the United States, the death toll was lower but still in the hundreds: at least 116 deaths with confirmed heat-related causes in Oregon (72 in Multnomah County), at least 112 in Washington and one in Idaho. ''The New York Times'' analysis suggested that almost 450 excess deaths in Washington and 160 deaths in Oregon occurred during the heat wave, though it has not been demonstrated how many were related to the heat. For comparison, however, Oregon had only 12 heat-related deaths 2017–2019. Most of the deaths occurred among the elderly.

On July 13, 2021, Multnomah County, Oregon published an analysis which found that a majority of deaths occurred in households which had no air conditioning or had only fans.

A surge in 9-1-1 calls and emergency department visits related to the heat saw 1,100 people were hospitalized in Oregon and Washington; and almost 2,800 heat-related emergency department visits were made on July 25–30. The Washington Department of Health estimated that over 2,000 such visits occurred statewide, not including visits to Veteran Administration or the military hospitals. In Portland, the number of calls and the response times doubled, setting a record for the area. On the other hand, in Oregon, while the number of heat-related visits skyrocketed, the total number of emergency visits stayed in the expected range. Non-emergency municipal services were also strained—on June 26, the non-emergency health information service (2-1-1) did not respond to 750 heat-related calls due to lack of working staff.

Some deaths also occurred among those seeking cooling in the Pacific Northwest's rivers. Two swimmers in Salem, who were trying to escape the heat, went missing in the Willamette River, another did so in Portland, while in Washington, three people drowned. With 30 deaths in King County, or was the deadliest weather event in the county. In fact, with 112 deaths, this became the deadliest weather event in Washington State history.

Impact

Air conditioning

The heat wave was a problem for major cities in the Northwest. Seattle and Portland had the lowest and third-lowest percentage of air-conditioned households among major metro areas in the United States, respectively. In 2015, a U.S. Census Bureau survey found that only 33% of Seattle homes have air conditioning (A/C) units, but that number increased to 44% in the 2019 survey, likely due to the warming trend in that area (Portland had 79% coverage, which was still below the national average). The rate of air-conditioned households was even lower in British Columbia despite marked increases over the years – BC Hydro estimated that only 34% of the province's residents were using these cooling appliances, while a separate analysis indicated that only 21% of Metro Vancouver's households used air conditioning in 2017 (the number was only slightly higher for Edmonton and Calgary, at 29% and 24%, respectively). Authorities therefore waived restrictions related to COVID-19 for designated cooling shelters in Oregon, Washington, and British Columbia.

Trying to stay cool, residents in the Pacific Northwest and Alberta rushed to buy A/C units, which significantly increased their prices (some double the normal), created long installation and delivery backlogs, and ultimately made them unavailable in many stores. The pent-up demand for cooling forced electricity consumption to soar to record-high summer values. BC Hydro reported a peak of 8,500  MW, AESO registered 11,721 MW (8 MW short of an all-time high), SaskPower recorded 3,547 MW, while several electricity providers in Washington also logged record values. It also prompted power utilities in Alberta, Idaho (Idaho Power) and eastern Washington (Avista) to formally ask to conserve energy. The warning had the Idaho State Capitol voluntarily turn off lights as a result, while in the Spokane area, power outages were rolled.

Some residents chose to shelter from the heat by booking rooms in hotels, which often ran out of air-conditioned accommodation. According to CoStar calculations, the search for cooled rooms made the hotel occupancy in British Columbia reach the highest levels since the beginning of the COVID-19 pandemic, while Washington County, Oregon (suburbs of Portland) hotels reported occupancy levels at or exceeding of total capacity on June 26–28, more than double the rate from 2020.

Infrastructure

The heat wave strained and damaged the region's infrastructure. It caused the sidewalks to buckle due to thermal expansion of concrete (57 sidewalks were damaged in Edmonton alone). In Washington and Oregon, damage was even more severe, leading to closures of roads and other inconveniences for drivers, including on some lanes of Interstate 5, as well as some state highways. In order to prevent thermal fatigue to Seattle's steel drawbridges, the city announced it would hose them down with cool water.

Public transportation also deteriorated during the sweltering conditions. Trains on Link light rail and Sounder commuter rail in Seattle operated at reduced speeds as a precaution against possible deformation of railroad tracks and overhead lines. In the Portland metropolitan area, TriMet suspended MAX Light Rail and WES Commuter Rail service for part of June 27 and all of June 28 because the cables from which the light rail cars drew electricity had sagged. Heat-induced rail distortion, called sun kink, slowed down the passenger service on the route of the Amtrak Cascades. Moreover, school districts in Kamloops, Sooke (BC), Ephrata and Royal City (WA) all suspended school bus services, while Grant County, Washington limited the frequency of the buses under their management as they did not offer air conditioning or the built-in version could not cope with the heat.

On June 28, 15 school districts in British Columbia's Lower Mainland, including all districts within Vancouver, closed due to the heat and their lack of sufficient cooling infrastructure; many others also changed, or shortened, Tuesday schedules to avoid daytime high temperatures. COVID-19 vaccination sites also endured disruption because of the weather conditions.

Businesses and workers

Local businesses faced a choice to continue to work under oppressive heat or make a day off. Some restaurants, food stands and cafés closed, fearing excessive heat at the workplace or spoilage of solid products. Similarly, numerous grocers were forced to shut down aisles and halt the sale of perishable goods or use plastic sheets as impromptu thermal shields, as refrigeration units failed under the load. The businesses that decided to stay open often provided ''de facto'' sheltering from heat or converted parts of buildings to cooling centers, such as Amazon.

In a few cases, workers in California and Oregon protested the lack of air conditioning and staged local walkouts, and agricultural trade unions had also noted increased calls to strike. An SMS survey among 2,176 farmworkers in Washington (mostly in the eastern part of the state) conducted by United Farm Workers, a labor union, reported that almost all farmers did not consider protections mandated by the state OSHA sufficient. Among the surveyed, about two-fifths reported not having had shade, just under a third not having received heat illness prevention training and a quarter of respondents had no access to cool water.

After Sebastian Francisco Perez, an outdoor farm worker in St. Paul, Oregon, died while at work, Oregon OSHA faced calls to enforce safety rules for dealing with the heat wave, which had been first drafted in May. In response, Oregon's governor, Kate Brown, directed the agency to enforce the safety regulations for 180 days pending permanent implementation. In Washington state, the heat wave prompted state agencies to roll out additional protections. ''The Washington Post'' reported that the federal Occupational Safety and Health Administration was also considering a set of heat-related safety rules, whose implementation was said to be a "top priority" for the Biden administration.

Culture and sports

Sports events were disrupted by the heat wave. In Eugene, where the qualifiers for the 2020 Summer Olympics were held, the heat caused evacuation of the stadium in the afternoon and postponement of some events to the evening hours, as the temperature of the stadium's track exceeded . It also caused an athlete to withdraw from the race.

Among other disruptions, a public swimming pool in Seattle's Rainier Beach neighborhood was closed due to dangerously high deck temperatures, so was a senior's center in Rathdrum, Idaho

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