Unprecedented Atmospheric River Causes Devastating Floods in Pacific Northwest

Beginning on December 8, 2025, an unprecedented atmospheric river unleashed torrential rains across the Pacific Northwest, leading to catastrophic flooding in Western Washington and British Columbia's Fraser Valley. The deluge displaced tens of thousands, caused extensive infrastructure damage, and reignited discussions on climate change's role in extreme weather events.

The Pacific Northwest is grappling with the aftermath of one of the most severe flooding events in recent history. Triggered by a prolonged and intense atmospheric river, the region has experienced record-breaking rainfall, leading to widespread evacuations, infrastructure failures, and significant economic disruptions. This disaster underscores the urgent need to address climate resilience and preparedness in vulnerable communities.

An atmospheric river is a narrow corridor of concentrated moisture in the atmosphere, capable of transporting large amounts of water vapor from tropical regions to higher latitudes. In this event, a persistent high-pressure system near California blocked incoming weather systems from moving southward, causing multiple low-pressure systems to stall and form an extreme atmospheric river aimed at the Pacific Northwest. This system was notable for its length, stretching approximately 7,000 miles from the Philippines to the Pacific Northwest, making it one of the longest observed globally.

In Washington, the Skagit River surged beyond historic levels, inundating towns like Burlington and Mount Vernon. Over 1,000 residents were forced to evacuate, with National Guard troops assisting in the efforts. Governor Bob Ferguson declared a statewide emergency on December 10, deploying the Washington National Guard to aid in disaster response. An estimated 100,000 people were under evacuation orders due to the anticipated impact of the floods.

The flooding led to widespread evacuations, infrastructure damage, and economic disruption. Emergency officials warned of ongoing risks, including mudslides, levee failures, and additional storms.

In British Columbia, Environment Canada issued warnings about impending heavy rainfall set to hit eastern Vancouver Island and coastal areas. Rainfall was particularly heavy in Abbotsford and Chilliwack in the Fraser Valley, with expectations of around 80 to 110 millimeters. On December 10, all highways connecting the Lower Mainland to the interior of the province were closed due to flooding, rockfalls, and avalanche risks.

The floods have had profound social and economic impacts. Thousands of residents were displaced, facing the loss of homes and livelihoods. Infrastructure damage, including road closures and power outages, disrupted daily life and economic activities. The agricultural sector, particularly in the fertile regions of the Fraser Valley and Skagit County, suffered significant losses due to inundated farmlands.

While strong atmospheric rivers are common in the Pacific Northwest during fall and winter, the intensity and duration of this event were exceptional. Similar events in recent history include the 2024 British Columbia floods and the 2021 Pacific Northwest floods. Atmospheric rivers account for 30–50% of the annual precipitation in the region, though most events are weaker. Climate change is likely contributing to the increased frequency and severity of such events.