The Unprecedented Pacific Northwest Heatwave of June 2021

Abstract

In late June to early July 2021 a heatwave of unprecedented magnitude impacted the Pacific Northwest region, lands colonially named British Columbia (BC) and Alberta (AB) in Canada, and Washington (WA) and Oregon (OR) in the United States. Many locations broke all-time maximum daily temperature records by more than 5°C. The standing Canadian national temperature record was broken on three consecutive days, at multiple locations, with the highest temperature of 49.6°C recorded, 4.6°C higher than the previous Canadian record. Weather forecasts provided advanced notice of the severity of the event, while sub-seasonal forecasts showed substantially increased likelihood of atmospheric blocking and high temperatures with 10-day lead times, and some skill out to 18 days. The impacts of this event were catastrophic. Estimates indicate at least 900 attributable deaths occurred across BC, WA and OR, likely the deadliest weather event in Canadian1 history. The heat contributed to mass-mortalities of marine life, reduced crop and fruit yields, river flooding from rapid snow and glacier melt, and a rapid increase in wildfires—the latter contributing to devastating landslides in the months following.

Optical properties of biomass burning aerosol during the 2021 Oregon fire season: comparison between wild and prescribed fires

“…16 The Pacic Northwest region of the US experienced an extreme heat wave event in late June 2021, setting all-time high temperature records and worsening drought conditions in many parts of Oregon. 17 The ensuing 2021 wildre season burned 3354 km 2 in Oregon, compared to the 2011-2020 average of 2677 km 2 burned per year, 18 contributing to signicant regional aerosol pollution.…”

Heatwaves Similar to the Unprecedented One in Summer 2021 Over Western North America Are Projected to Become More Frequent in a Warmer World

“…DONG ET AL. 10.1029/2022EF003437 2 of 14 From late June to early July 2021, an unprecedented heatwave impacted western North America (WNA) (Lin et al, 2022;Neal et al, 2022;Philip et al, 2021;Qian et al, 2022;White et al, 2022). The temperature anomalies in multiple cities were about 20°C higher than average in late June (The Verge, 2021).…”

Evidence of increased mussel abundance related to the Pacific marine heatwave and sea star wasting

“…Although water and air temperature has direct effects on mussel physiology (Zippay & Helmuth, 2012), we did not detect a strong direct effect of water temperature, water temperature anomaly, or mean exposure to extreme high or low air temperature on mussel metrics. The lack of significant effect of these temperature metrics on mussels could reflect (1) direct effects were masked by other (White et al, 2022). Throughout our study period, exposure time to air temperatures ≥25°C was low and no mass mortality events were observed at our study sites.…”

“…Lab experiments on M. trossulus stress responses to heat have used treatment temperatures far above the seasonal mean temperatures during the PMH at our study sites (21–32°C) (Lockwood & Somero, 2011; Tomanek & Zuzow, 2010). A mass mortality event of M. trossulus occurred in British Columbia in 2021 when low tides coincided with high air temperatures and rock surfaces along the shoreline exceeded 50°C (White et al, 2022). Throughout our study period, exposure time to air temperatures ≥25°C was low and no mass mortality events were observed at our study sites.…”