2021 Western North America heat wave: Difference between revisions

2021 Western North America heat wave

Air temperature anomalies across North America on June 27, 2021, compared to 2014-2020 baseline
Date	Late June 2021 (2021-06) – present
Location	Canada  United States
Type	Heat wave
Deaths	613+ total ~480+ heat-related deaths in British Columbia, Canada; 133+ in the United States[1]

An extreme, ongoing heat wave in Western North America began affecting much of the Pacific Northwest and Western Canada in late June 2021. The heat has affected northern California, Idaho, western Nevada, Oregon, and Washington in the United States, as well as British Columbia, and, in its later phase, Alberta, Manitoba, the Northwest Territories, Saskatchewan, and Yukon, all in Canada.^[2] It has also affected inland regions of central and southern California,^[3] northwestern and southern Nevada and parts of Montana and Wyoming, though the temperature anomalies were not as extreme as regions farther north.

The heat wave appeared due to an exceptionally strong ridge centered over the area, whose strength has been asserted to be an effect of climate change.^[4] It resulted in some of the highest temperatures ever recorded in the region,^[5] including the highest temperature ever measured in Canada at 49.6 °C (121.3 °F).

The heat wave has sparked numerous extensive wildfires, reaching hundreds of square kilometers in area, which have led to widespread disruption on the roads. One of them largely destroyed Lytton, British Columbia, the village where the record-high temperature for Canada had been set. The heat also caused damage to the road and rail infrastructure, forced closures of businesses, disrupted cultural events and triggered extensive melting of snowcaps, some of which resulted in flooding.

The exact death toll is still unknown, but growing. On July 2, 2021, the chief coroner of British Columbia said about 480 more sudden deaths than usual were reported in the province, suggesting the majority or all of them could have died as a result of the heat.^[6][7] Deaths in the United States include at least 95 in Oregon (of which 59 are in Multnomah County, which includes Portland)^[8][9][10] and at least 38 in Washington.^[11]

On June 23, the United States National Weather Service warned of an approaching heat wave in the Pacific Northwest,^[12] whose origins could be traced to torrential rains in China.^[13] There, the warm, moist air rose and was eventually sucked up 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,^[14] forced to accommodate the high-pressure area south of the jet stream's meander.^[15] At the same time, the Southwestern states were enduring an intense drought,^[16] which had earlier allowed higher-than-average temperatures over the Southwestern United States, leading to a similar hot wave earlier in June.^[17][18] Its remnants then moved north to the Pacific Northwest.^[19][20] Six days later, Environment Canada issued a heat warning for Alberta, Saskatchewan, British Columbia, Manitoba, Yukon, and Northwest Territories.^[21]

These conditions made way for a massive Rex block,^[25][18] which is more often formed during La Niña years.^[15] 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.^[22] As the Pacific Northwest, just as the Southwest, experienced severe drought conditions, the already warm air was heating more quickly than usual,^[26] which intensified the ridge so strongly it caused a heat dome.^[5] Indeed, on June 27, the height at which 500 hPa air pressure was sustained (geopotential height) was reported at 5,986 m (19,639 ft) in Prince George, British Columbia – the highest ever recorded in the area; adjacent stations have similarly reported record-high values.^[27] The downslope winds from the Cascades and other mountain ranges further warmed the air in the valleys.^{[20][24][28][29]}

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.^[30][31] At this stage, the heat was kept between the warm and cold fronts of the low-pressure area that had formed over southern Northwest Territories and transported eastward towards Hudson Bay.^[32] Sweltering conditions were expected in the coming days as far east as Montana,^[33] Manitoba,^[34] and in extreme Northwest Ontario,^[35] though the temperatures were not expected to be as high.^[36][37]

Climate change in Canada and in the United States are widely considered to be the major causes of the heat wave's unprecedented intensity and duration,^{[4][38][39][40][41][42]} although whether the frequency of these omega blocks is due to global heating is not yet known.^[5] Based on historic data, several meteorologists noted that this phenomenon could be expected to occur only once over several thousand years.^[5][43]

Much of the Pacific Northwest, normally known for its temperate weather in June, received maximum temperatures 11-19 °C (20-35 °F) above normal during this heat wave.^{[44][45][46][47]} 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.^[44][48][49]

The highest temperatures of the heat wave were registered in British Columbia, but other provinces and territories have also suffered. As of June 29, 103 all-time heat records were set across Western Canada.^[50]

In Alberta, the highest heat was observed in the period from June 29 to July 1.^[51][52] Banff 37.8 °C (100.0 °F), Beaverlodge 40.5 °C (104.9 °F), Cochrane 35.0 °C (95.0 °F), Jasper 41.2 °C (106.2 °F), Grande Prairie 41.5 °C (106.7 °F), Hendrickson Creek 38.3 °C (100.9 °F), Nordegg 37.2 °C (99.0 °F) and Red Earth Creek 40.1 °C (104.2 °F) have all seen the strongest heat ever measured in these communities, most after breaking all-time records of the previous day.^[53] Calgary noted 36.3 °C (97.3 °F) on June 29 and July 1, which stopped just 0.2 °C short of the highest observed temperature ever and beat the all-time records for June and July.^[54][55]

On June 29, the temperature in Lytton, British Columbia, hit 49.6 °C (121.3 °F), the highest temperature ever recorded in Canada,^[56] though a nearby more modern station reported that the extreme was 1 °C lower.^[57] The stations were destroyed by the Lytton wildfire the next day. The record occurred after consecutively setting new record highs of 46.6 °C (115.9 °F) on June 27 and 47.9 °C (118.2 °F) on June 28.^[58] 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 record highs of Europe or South America.^[59][60]

On June 27, local records were set in areas such as Cultus Lake, Lillooet,^[61] Ashcroft (43.8 °C (110.8 °F))^[62] and Kamloops (44 °C (111 °F));^[63] in all, there were 59 weather stations in B.C. that set records for hottest temperatures recorded for June 27.^[64] These were largely beaten in the following days (Kamloops, for instance, has registered 45.8 °C (114.4 °F) on June 28 and 47.3 °C (117.1 °F) on June 29).^[56][65][66] On June 28, records were set in Abbotsford at 42.9 °C (109.2 °F), Victoria at 39.8 °C (103.6 °F) and Port Alberni at 42.7 °C (108.9 °F).^[50]

Manitoba has seen most of the heat records concentrated in the northern parts of the province. A remote community of Tadoule Lake has observed 38.1 °C (100.6 °F), beating the previous all-time record by 6.2 °C (11 °F),^[67] so did Lynn Lake (38.0 °C (100.4 °F)),^[68] while Churchill, on the shore of Hudson Bay, registered 34.1 °C (93.4 °F), the highest temperature for July.^[68]

Southern parts of the province, including Winnipeg, are expected to see the highest temperatures on July 3.^[69]

On June 28, Nahanni Butte set a regional record at 38.1 °C (100.6 °F).^[58] Two days later, Fort Smith, just north of the border with Alberta, hit 39.9 °C (103.8 °F), which beat the previous all-time territorial record, registered in the same place in 1941.^[70][71][72]

In a similar way to Manitoba, the majority of heat records (including all-time highs) have been noted in the northern parts of the province. Stony Rapids saw the heat soar to 39.8 °C (103.6 °F) on 30 June,^[73] an all-time high, with unprecedented temperatures also set in Key Lake Airport, sometimes dubbed "the cold pole of Saskatchewan",^[74] and Collins Bay Airport on July 1, both at 37.0 °C (98.6 °F),^[51][68] as well as in Uranium City (38.0 °C (100.4 °F)).^[75] July highs were also observed in these settlements on the first day of the month,^[76] when 26 daily records were set across the province, most in northern communities.^[77]

Elsewhere, the heat has arrived slightly later. Saskatoon reached 35.4 °C (95.7 °F) on July 1^[77] and beat the month record the following day, at 40.5 °C (104.9 °F), a tenth of degree less than the all-time record.^[78] La Ronge, according to preliminary data, has also surpassed the July record, reaching 35.4 °C (95.7 °F).^[79]

Several major cities, including Seattle, Portland, and Spokane, experienced high temperatures far exceeding 100 °F (38 °C) and low temperatures higher than the area's normal daily high temperatures.

The hottest temperature during the heat wave in the United States was noted in Peshastin in Chelan County, Washington, where temperatures soared to 119 °F (48 °C) on June 29, slightly surpassing the previous all-time high for the state.^[80][81][82] Southeastern parts of Washington's interior were almost as hot, tying the previous 118 °F (48 °C) mark.^[43][83] Preliminary data suggests that a station at Alpowa Creek near Clarkston, Washington, reached 122.9 °F (50.5 °C) the same day, but this remains to be confirmed.^[84]

Being largely on the margin of the high pressure dome, Idaho has not seen temperatures as extreme as elsewhere.^[42] In Lewiston, on the border with Washington, 115 °F (46 °C) 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.^[85] Other localities in the Treasure Valley to the east are expected to sustain triple-digit heat for a solid week (which is in and of itself unusual) and in general to tie or beat daily records,^[86] such as in Boise, which tied one for June 29 (105 °F (41 °C))^[87] and for June 30 (105 °F (41 °C)).^[88] Records were also beaten in the Idaho Panhandle, with Coeur d'Alene registering 109 °F (43 °C), which surpassed the previous highest temperature for June and equaled the all-time high for the city.^[43]

On June 26, Portland broke its previous all-time record high temperature of 107 °F (42 °C), set in July 1965 and August 1981, with a temperature of 108 °F (42 °C).^[89] It topped that record again on June 27, with a temperature of 112 °F (44 °C).^[90] The following day, the temperature increased further to 116 °F (47 °C).^[46][91] All of these extremes also beat the previous record June temperature, which was 102 °F (39 °C) set on June 26, 2006.^[45]

Salem, Oregon, reached 105 °F (41 °C) degrees on June 26, its record high temperature for June. It then hit 113 °F (45 °C) degrees on June 27, breaking the record for the highest temperature ever recorded in that city, which was previously 108 °F (42 °C). Salem then exceeded the previous day's record temperature on June 28, with a maximum temperature of 117 °F (47 °C).^[92] However, not all the regions of the mid-Willamette Valley received extreme heat on June 28, especially regions south of South Salem where temperatures only reached the mid-90s Fahrenheit, likely due to the sea breeze in the area.^[93]

The Willamette Valley has also seen extreme overnight temperature drops (twice the size of normal fluctuations) due to cooler air coming from the ocean – Portland cooled a record 52 °F (29 °C) during the night, while Salem almost approached its all-time largest temperature swing, from 117 °F (47 °C) to 61 °F (16 °C).^[94]

Between 1894, when the records in Seattle began, and June 2021, temperatures over 100 °F (38 °C) were only noted three times;^[95][96] however, the Seattle-Tacoma International Airport has recorded three consecutive days of temperatures over 100 °F (38 °C).^[97] Notably, they rose to 104 °F (40 °C) on June 27, only to be beaten to 108 °F (42 °C) the following day.^[98][99] All of these values have broken the previous June record (96 °F (36 °C), 2017) by a large margin.^[45] The suburbs farther from the coast were even hotter – a local radio station in Maple Valley reported temperatures of 118 °F (48 °C).^[100]

On June 26, Port Angeles recorded an all-time record high of 95 °F (35 °C).^[101] The Quillayute Airport weather station, also on the Olympic Peninsula, reported 110 °F (43 °C) on June 28, exceeding its prior record by 11 °F (6 °C).^[48]

On Mount Rainier, normally freezing temperatures reached 73 °F (23 °C) degrees above 10,000 feet (3,000 m) on June 27.^[102] The heat wave is blamed for greater glacier melt on Mt. Rainier than had been seen in the state in the past 100 years.^[103]

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.^{[104][105][106]} On June 29, Spokane, Ephrata and Omak all reached their all-time records, at 109 °F (43 °C), 115 °F (46 °C) and 117 °F (47 °C), respectively. These are the hottest temperatures measured since records began for those areas.^{[107][108][109]} Extremely warm minimal temperatures were also noted: Ephrata's thermometers did not go lower than 78 °F (26 °C) on June 28^[110] and 82 °F (28 °C) on June 29,^[111] and all-time highest low temperature records were set at Spokane International Airport on June 29 (77 °F (25 °C)) and June 30 (78 °F (26 °C)).^[112][113]

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 118 °F (48 °C), tying the then all-time record for the state of Washington and beating the June statewide record by 5 degrees Fahrenheit.^[43] The same heat was measured in Tri-Cities on June 28–29.^[114][115] On June 29, temperatures of 119 °F (48 °C) were recorded in Chelan County at Peshastin and Ardenvoir, setting a new statewide heat record.^[80]

The heat wave is 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.^[116] 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.^[45] The rate of air-conditioned households is 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,^[117] while a separate analysis indicated that only 19% of Metro Vancouver's households used air conditioning in 2017.^[118] For these reasons, authorities have waived restrictions related to COVID-19 for designated cooling shelters in Oregon,^[119] Washington,^[120] and British Columbia.^[121]

The extreme heat and dry conditions has led to calls of scientists, firefighters and various politicians not to use fireworks during Independence Day celebrations in the Western United States^[122] and on Canada Day in Alberta.^[123]

In British Columbia, 103 more deaths than expected in a four day period were referred to the coroner up to June 29,^[124][125] with the number rising to 321 the following day,^[126] and to about 480 two days later.^[7] The chief coroner of the province also noted that in the five years preceding the event, the province had had only three casualties related to heat.^[126] Due to unprecedented emergency call volume, emergency services left behind bodies of victims as the police and ambulances continued to respond to other calls. E-Comm emergency dispatchers answered nearly 15,300 calls on June 26 and 27; this is about 55 percent above normal for the month.^[124] From June 25–28, British Columbia Emergency Health Services ambulances responded to 187 heat exhaustion calls and 52 heat stroke calls.^[127]

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;^[128][129] many have also changed, or shortened, Tuesday schedules to avoid the heat.^[130] COVID-19 vaccination sites have also endured disruption because of the weather conditions.^[130]

The heat wave caused rapid snowmelt of some of the Rocky Mountains snowcaps, which triggered a week-long evacuation order in the Pemberton Valley due to rising water levels;^[131] extreme water rises were also noted in Squamish^[132] and alerts issued in other places in the province.^[133] It has also made electricity demand soar to levels never seen before – BC Hydro reported consumption levels reaching 8,500 MW.^[134]

The extreme heat led to exceptionally dangerous wildfire conditions,^[127] which led Mike Flannigan, a University of Alberta wildfire scientist, to say that the summer fire season could be "horrific" if the extreme conditions persisted.^[135] At least 19 wildfires ignited between June 27 and 29, but most remained under 5 hectares (12 acres);^[135] one fire, however, grew to at least 2 km² (0.77 sq mi) by June 29, prompting evacuations.^[127] On June 30, further orders were given, when two large fires spread out of control – the one near Kamloops Lake grew to 200 km² (77 sq mi) as of the evening of June 30, and the other one, north of Lillooet, has similarly measured tens of square kilometers.^[136][137] In addition to that, pyrocumulus clouds formed due to such extensive burning, producing several hundred thousand lightning strikes and further complicating efforts to contain fires.^[138]

On July 3, 2021 firefighters were battling more than 170 wildfires and the military were on stand-by to respond at any indication. Fires raged in the town of Boston Bar, which is located near Lytton.^[139]

In the evening the same day, Lytton, the settlement that had been beating national heat records in the previous days, along with several First Nations reserves, were ordered to be evacuated as a wildfire was approaching to the village, where it later has done widespread destruction to the buildings,^{[140][141][142]} which a local MP, Brad Vis, has estimated at 90%^[143] and damaged roads, telecommunication and power facilities as well as the railway that comes through the settlement;^{[141][144][145]} at least two people died while hiding from the flames.^[146] The fire in the settlement has forced closure of a section of British Columbia Highway 1, part of Trans-Canada Highway, as well as Highway 12, which ends in Lytton.^[137][143]

Agriculture has also seen losses. Raspberry farms in the Lower Mainland and lettuce producers in the Okanagan Valley were reported to be struggling with spoilt crops.^[1][147]

AESO, the Albertan electricity regulator, noted demand inching towards an all-time high (11,721 MW), which prompted the operator to formally ask consumers to conserve energy.^[148] Additionally, Beaumont issued a mandatory ban on non-essential water usage, citing drought conditions.^[148]

In southern Alberta, the heat has set fire to the wheat fields in some places, which, combined with a severe drought in the province, has put the harvest in jeopardy.^[1]

The heat wave inflicted damage on the infrastructure across the Pacific Northwest. Roads, including Interstate 5, began to buckle due to thermal expansion, leading to closures and other inconveniences for drivers.^{[149][150][151][152][153]} Heat induced rail distortion, called sun kink, on the route of the Amtrak Cascades required operation of the passenger train at a slower than normal speed.^[154] Moreover, the event has sparked significant fires across the West Coast, such that 9,000 firefighters were deployed to extinguish them.^[155]

Most parts of the state were spared from the highest temperatures recorded, but extreme drought conditions have facilitated widespread wildfires. In extreme north California, three large fires have erupted: the Lava Fire burning west of Mount Shasta, caused by a lightning strike on 25 June,^[156][157] "Tennant Fire" in Siskiyou County^[158] as well as "Salt Fire" in Shasta County, north of Redding.^[159] Strong winds, which were causing fire tornadoes in some places,^[160] and dry vegetation have hampered efforts to contain the fires, which has led to closures on U.S. Route 97.^[158][161] The winds were so strong that residents of Medford, Oregon, ca. 81 mi (130 km) north of the fires, reported having seen ash falling from the sky.^[162]

The Lava Fire, which has reached an area of nearly 24,000 acres (97 km²), has prompted an evacuation of 3,500 residents in the vicinity.^{[157][163][164]}

Idaho has not seen record high temperatures, nor has the heat wave caused any deaths, but it has caused some disruption. Idaho Power, an electric utility serving most of the state, has formally asked residents to conserve energy in the peak hours,^[165] and the Idaho State Capitol has voluntarily switched off lights as a result.^[166] The heat has also led to a temporary closure of a senior center in Rathdrum^[167] and postponement of some local cultural activities.^[168]

Additionally, the population of sockeye salmon in Idaho was found to be threatened by the increasing water temperatures, which prompted preventative measures to avoid damage to the ecosystem.^[169]

At least 94 people have died due to the heat-related causes, compared to 12 dead overall in the period from 2017 to 2019.)^[8][9][10] Of these deaths, 59 occurred in Multnomah County, which includes Portland, 12 in Marion County (Salem), ten in Clackamas County, eight in Washington County, two in Deschutes County (Bend), while Columbia, Umatilla and Polk counties have each registered one death.^[9] Of the victims of the current extreme weather, two swimmers in Salem, who were trying to escape the heat, went missing in the Willamette River,^[92] and two homeless people died in Bend on June 28.^[170]

In Eugene, where the qualifiers for the 2020 Summer Olympics were held, the heat caused evacuation of the stadium and postponement of some events to the evening hours, as the temperature of the stadium's track exceeded 150 °F (66 °C).^[171][172] It also caused an athlete to withdraw from the race.^[172]

Salem recorded at least 30 heat-related injuries throughout the heat wave. 22 of those injuries occurred from June 25 to 27 and an additional 12 injuries occurred on the afternoon of June 28. An increase in heat-related illnesses was also reported statewide throughout Oregon during the heat wave.^[92]

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 as the cables from which the light rail cars drew electricity had sagged.^[173][174]

Due to the "imminent risk" of wildfires and with no rain in sight, Governor Kate Brown has declared a state of emergency.^[175][176] The fires have forced an airport in Redmond to close and had residents in different communities across the state evacuated.^[177]

In King County, home to Seattle, thirteen people are known to have died from the heat as of June 30. Three more casualties were reported in Snohomish County, nine in Pierce County, four in Thurston County, seven more in Spokane, and 3 additional deaths in Okanogan County.^{[11][113][178] [179]}Most of the deaths occurred among the elderly.^[180] There were at least three victims of drowning, who were trying to escape from the heat.^[181] Moreover, almost 1,800 people have turned over for medical advice, suspecting heat-related illnesses until July 1.^[8]

A public swimming pool in Seattle's Rainier Beach neighborhood was closed due to dangerously high deck temperatures.^[182][183] The city announced it would hose down steel drawbridges with cool water to prevent them from getting stuck due to thermal expansion.^[184] Trains on Link light rail and Sounder commuter rail operated at reduced speeds, as railroad tracks and overhead lines may deform under the extreme heat.^[185] In Eastern Washington, power outages were reported in Spokane, some of which were done in order to reduce the load on the electrical systems.^{[186][187][188][189]} Some of the local businesses have also closed due to the heat.^[190][191]

10 million pounds of fruit a day were being harvested in the Pacific Northwest at the time the heat wave struck.^[192] Farmers in Eastern Washington facing a loss of the cherry crop sent workers into orchards at night for their health safety.^[193][194] The raspberry crop in Whatcom County, Washington, 85% of the nation's total production, was endangered.^[195]

In Seattle, nearly a hundred juvenile terns whose nests were on top of an industrial building died when they plunged to the pavement below. Investigators from the Washington Department of Fish and Wildlife believe that the birds, too young to fly, were trying to escape the heat on the roof. The birds that survived the fall were treated for burns on their feet from the asphalt.^[196]

Numerous grocers have been forced to shut down aisles and halt the sale of perishable goods (and/or use plastic sheets as de facto thermal shields) as refrigeration units failed under the load. In some cases they employed their rooftop sprinkling systems. Similarly, several restaurants and cafés closed due to refrigeration and air conditioning issues and concerns over the welfare of staff.^[197]

• 2020–21 North American drought
• 2021 wildfire season

• Baker, Mike (June 25, 2021). "Air-Conditioning Was Once Taboo in Seattle. Not Anymore". The New York Times. An intense heat wave is set to torment the Pacific Northwest. Many who have always done without air-conditioners are scrambling to get them now.
• Josie Fischels (June 29, 2021). "Northwest heat wave melts power cables, buckles roads". NPR.
• Rachel Ramirez (June 29, 2021). "The Northwest heat wave is 'unprecedented.' Here's what's pushing it into uncharted territory". CNN.
• "How Weird Is the Heat in Portland, Seattle and Vancouver? Off the Charts". The New York Times. June 29, 2021. The heat smothering the Pacific Northwest has little precedent in at least four decades of record keeping. {{cite news}}: Unknown parameter |authors= ignored (help)
• "Historic Northwest heat wave linked to dozens of deaths and hundreds of emergency room visits". CNN. June 29, 2021. {{cite news}}: Unknown parameter |authors= ignored (help)

• Media related to 2021 Western North America heat wave at Wikimedia Commons