The unprecedented Pacific Northwest heat-wave of June 2021

In late June 2021 a heatwave of unprecedented magnitude impacted the Pacific Northwest region of Canada and the United States. Many locations broke all-time maximum temperature records by more than 5 °C, and the Canadian national temperature record was broken by 4.6 °C, with a new record temperature of 49.6 °C. The study provides a comprehensive summary of the event and its impacts. Upstream diabatic heating played a key role in the magnitude of the anomaly. Weather forecasts provided advance notice, while subseasonal forecasts showed an increased likelihood of a heat extreme with lead times of 10–20 days. Impacts were catastrophic, including hundreds of attributable deaths across the region, mass mortalities of marine life, reduced crop and fruit yields, river flooding from rapid snow and glacier melt, and a substantial increase in wildfires that contributed to landslides in the following months. These impacts illustrate how climate change can be devastating.

Rachel H. White, Sam Anderson, James F. Booth, Ginni Braich, Christina Draeger, Cuiyi Fei, Christopher D. G. Harley, Sarah B. Henderson, Matthias Jakob, Carie-Ann Lau, Lualawi Mareshet Admasu, Veeshan Narinesingh, Christopher Rodell, Eliott Roocroft, Kate R. Weinberger, Greg West