By Steven Schauer, Deputy Executive Director

A powerful atmospheric river brought several days of heavy rainfall to King County from March 17 through March 21, 2026, causing a prolonged flood event that affected multiple rivers across the county and prompted nearly four full days of continuous activation at the King County Flood Warning Center. The Flood Warning Center is funded by the King County Flood Control District and staffed by King County.

During the event, rivers including the Snoqualmie, Tolt, White, Cedar, South Fork Skykomish, and Green all reached flood alert phases, with the Snoqualmie and Tolt rivers reaching Phase 3, or moderate flooding, on more than one occasion.

Flood Warning Center opens as rivers begin to rise

Ahead of the event, the National Weather Service issued a Hydrologic Outlook on March 16 and a Flood Watch on March 17, signaling the potential for flooding across King County. That evening, the Snoqualmie River reached Phase 2 flood stage, prompting King County to open the Flood Warning Center remotely at about 7:40 p.m. on Tuesday, March 17. The center then operated continuously until closing at 5 p.m. on Saturday, March 21.

When the Flood Warning Center opened, the Snoqualmie River had risen above the Phase 2 threshold, with minor flooding possible in low-lying areas and on roads including Southeast Reinig Road, Meadowbrook Road, Mill Pond Road, Neal Road Southeast, Southeast 20th Street, West Snoqualmie River Road Northeast north of Northeast 18th Street, and Northeast Tolt Hill Road.

Multiple rivers enter flood phases

By early Wednesday, March 18, the Tolt and White rivers had joined the Snoqualmie River at Phase 2. The Tolt River reached Phase 2 at 3:30 a.m., creating the potential for levee seepage along the south bank between the Snoqualmie Valley Trail bridge and State Route 203. The White River reached Phase 2 at 4:45 a.m., raising concerns about overbank flooding near Government Canal, Pacific City Park, and HESCO flood protection barriers in the City of Pacific. At the same time, both the Cedar and Green rivers had reached Phase 1, an internal alert stage used to monitor changing conditions.

Later that same morning, conditions worsened. The Tolt River reached Phase 3 at about 7:45 a.m., bringing the potential for water over sections of Tolt River Road Northeast, seepage, and backyard flooding near the levee along the south bank of the river. About two hours later, the Snoqualmie River also rose into Phase 3, indicating moderate flooding across the Snoqualmie Valley and the potential for additional road closures, including West Snoqualmie River Road Southeast south of Southeast 19th Street, Northeast 8th Street, and Northeast 138th Street.

With both rivers in Phase 3, King County deployed flood patrols along the Tolt and Snoqualmie rivers. Flood patrol members are specially trained Department of Natural Resources and Parks employees who monitor levees and report conditions back to the Flood Warning Center during significant flood events.

Flooding continues into Thursday and Friday

Although some rivers briefly receded on Thursday, March 19, the flood threat remained elevated. The National Weather Service issued a Flood Warning for the Snoqualmie and Tolt rivers, while a Flood Watch remained in effect for the county. That evening, the Cedar River reached Phase 2 at Landsburg, where flows passed 2,800 cubic feet per second. Minor flooding was possible along the river east of Renton, including near Southeast 184th Street and Lower Dorre Don Way Southeast.

Early Friday, March 20, the Snoqualmie River rose into Phase 3 for the second time during the week, reaching 20,630 cubic feet per second and again bringing the potential for flooding of varied depths across the Snoqualmie Valley. Soon after, the Tolt River also returned to Phase 3.

At that point, the White and Cedar rivers remained at Phase 2, while the South Fork Skykomish had reached Phase 2 as well. Later Friday afternoon, the Green River also climbed to Phase 2 upstream of Auburn, though no impacts were expected in the City of Auburn or farther downstream in the Green River Valley.

Throughout the event, people were directed to the Flood Warning System and MyCommute resources for current river forecasts and road closure information. Flood Patrol teams remained active where Phase 3 conditions required on-the-ground monitoring.

Event winds down after nearly four days of activation

As rainfall eased and river levels began to recede in the upper basins, King County closed the Flood Warning Center at 5 p.m. on Saturday, March 21. By that time, the center had been activated for nearly four full days, serving as an around-the-clock information clearinghouse for the public and partner agencies responsible for public safety during the flood event. Staff continued monitoring river and weather conditions after closure in case conditions changed unexpectedly.

Staying prepared

This flood event was another reminder that flood season in King County can continue well into spring when strong atmospheric rivers bring prolonged rainfall and rapidly rising river conditions. The King County Flood Control District offers everyone free access to KC Flood Alerts, an automated system that sends customized flood notifications by email, text, or voicemail for major river systems. Signing up can provide valuable time to prepare when rivers begin to rise. KC Flood Alerts is operated by King County as service provider to the King County Flood Control District.

For more information and to sign up for alerts, visit the King County Flood Control District’s Be Flood Ready resource page.