The unprecedented Pacific Northwest heatwave of June 2021

The 2021 unprecedented Pacific Northwest heatwave broke temperature records by extraordinary amounts. Impacts included hundreds of deaths, mass-mortalities of marine life, increased wildfires, reduced crop and fruit yields, and river flooding. 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 & DEG;C, and the Canadian national temperature record was broken by 4.6 & DEG;C, with a new record temperature of 49.6 & DEG;C. Here, we provide a comprehensive summary of this event and its impacts. Upstream diabatic heating played a key role in the magnitude of this anomaly. Weather forecasts provided advanced notice of the event, while sub-seasonal forecasts showed an increased likelihood of a heat extreme with lead times of 10-20 days. The impacts of this event were catastrophic, including hundreds of attributable deaths across the Pacific Northwest, mass-mortalities of marine life, reduced crop and fruit yields, river flooding from rapid snow and glacier melt, and a substantial increase in wildfires-the latter contributing to landslides in the months following. These impacts provide examples we can learn from and a vivid depiction of how climate change can be so devastating.

Automated summary

The unprecedented 2021 heatwave in the Pacific Northwest region broke temperature records by extraordinary amounts. The impacts were catastrophic, causing deaths, mass-mortalities of marine life, wildfires, reduced crop yields, and river flooding.