BELLINGHAM, WA (MyBellinghamNow.com) – Residents are being warned of a water quality alert at a popular Bellingham lake.

RE Sources says it detected large algae blooms at Lake Padden during its monthly monitoring on Tuesday, Sept. 15.

The environmental nonprofit found the blooms near the boat launch and on the northwest end of the lake near the tennis courts.

It’s unclear how long the algae bloom has been present at the lake.

RE Sources conducts monthly monitoring at Lake Padden and says the last bloom there was observed in February 2026. Its most recent monitoring before Tuesday came on Aug. 18, when it did not note any signs of an algae bloom.

A member of the My Bellingham Now staff noticed similar blooms to the ones most recently reported at the lake on Aug. 24.

An algal bloom near the Lake Padden tennis courts on Aug. 24, 2026. Photo by Emma Toscani

RE Sources is advising people and their pets to avoid all algae in the area, which looks like spilled green paint on the water’s surface.

The nonprofit sent an algae sample to the King County Environmental Lab for a toxin level test. Results are expected to be released by Friday, Sept. 18, or the following Monday.

The City of Bellingham and the county’s health department have regularly advised against touching any algal blooms at Lake Padden out of an abundance of caution.