A powerful atmospheric river brought record rainfall to parts of Washington and Oregon states in the Pacific Northwest of the USA from 04 December 2023.

As of 05 December, two fatalities were reported. Dozens of homes have been flooded and several people rescued, including some by Coast Guard Helicopter teams.

Floods in Snohomish County, Washington State, USA, December 2023. Photo:  Snohomish County Sheriffs Office

Rain and Rivers

The National Weather Service (NWS) in Seattle reported significant rainfall totals in various parts of Western Washington, including the Olympic National Park which recorded 8.67 inches / 220.22 mm of rain in 24 hours to 05 December 2023. Weather stations at Hoodsport and Duvall both recorded 7.12 inches / 180.85 mm during the same period.

24-hour rainfall totals in Washington, USA, 04 to 05 December 2023. Image: NWS Seattle

NWS Seattle also reported daily rainfall records in Hoquiam, Forks, Sea-Tac Airport and Olympia Airport. The 4.69 inches / 119.126 mm of rain that fell in 24 hours in Forks, WA, is more than double the previous daily rainfall record set in 1971, and more rain than Las Vegas, NV has received in all of 2023 so far.

The Stillaguamish River reached a record high of 21.34 feet / 6.50 metres at Arlington on 05 December, beating the previous high of 21.16 feet / 6.44 metres reached in 2010.

As of 05 December, the Skagit River was above Major Flood stage near Concrete. The Snohomish, Snoqualmie, Skokomish and Cowlitz were above Moderate Flood Stage in several locations.

The Skagit River near Concrete WA, USA, December 2023. Image: NWS / NOAA

The Stillaguamish River at Arlington, WA, USA, December 2023. Image: NWS / NOAA

Rescues and Flood Damage

The US Coast Guard helicopter teams rescued four people from a flooded home and another person from a vehicle trapped in flood waters near Rosburg, Washington, on 05 December.

Fire crews recued 4 people from a flooded home on Monroe, Washington. Another person was rescued from a vehicle trapped in floods in Granite Falls, Washington, where at least 12 homes have been flooded.

The settlement of Silvana in Washington was left isolated and only reachable by boat after roads were swamped. Fire department officials asked 200 residents to shelter in place.

In Oregon, Washington County Sheriff’s Office reported the body of a person believed to have been swept away by floods was found in the Bronson Creek in Beaverton near Portland. In a separate incident, another body was recovered from the swollen Johnson Creek in Portland. Teams from police and Portland Fire and Rescue were deployed to search the area after a man was reported missing on 04 December.

Parts of coastal US Highway 101 in Oregon were closed due to flooding. Some schools were also closed in Oregon. The worst affected areas are in Tillamook County where more than 30 homes have been flooded in Rockaway Beach.

Floods in Washington State, USA, December 2023 – Snohomish County Sheriffs Office

Flooding along the South Fork Stillaguamish River in Washington, USA, 05 December 2023. Photo: Snohomish County