Swimmers and boaters at Matthews Beach Park in North Seattle lost access to the water Sunday, Sept. 27, after Seattle Public Utilities reported a sewage overflow along the Lake Washington shoreline.

SPU posted closure signs at the beach and at Sail Sand Point, a nonprofit community boating center inside Magnuson Park. The signs will stay up for seven days, according to KIRO 7. SPU has not announced a specific reopening date, but the seven-day window puts the earliest possible lifting at Sunday, Oct. 4.

No swimming and no launching from Sail Sand Point's shoreline until the closure lifts.

Sail Sand Point canceled open boating on Sunday, Sept. 27, and Monday, Sept. 28, and called off Sunday afternoon racing. The center said on its website that it would contact participants in its race team and Adult 101 classes directly. SPU said it would also reach out to race participants.

Anyone who still needs water access during the closure can use the public boat launch on the south side of Magnuson Park, according to Sail Sand Point.

Health risks

Public Health – Seattle & King County has warned that swimming in water with elevated bacteria levels can cause nausea, stomach cramps, diarrhea, eye infections and skin rashes. Children, pregnant people, older adults and people with compromised immune systems face the greatest risk.

Sewage-overflow closures are distinct from the more common wildlife-bacteria closures that happen during summer swim season, according to the county health agency.

Second closure this year

This is not the first time SPU has shut down Matthews Beach in 2026. Seattle Parks and Recreation posted a warning on March 31 about a separate contamination event at the same park. That closure lasted until April 4.

SPU has not disclosed the cause of the Sept. 27 overflow or the volume of sewage released. No specific reopening date has been announced beyond the seven-day sign posting window.