The Oregon Health Authority lifted its advisory after water monitoring confirmed cyanotoxin levels in Ross Island Lagoon and the Willamette River were below recreational guideline values for people. OHA advised continued vigilance for signs of cyanobacteria blooms because they can develop and disappear rapidly when conditions are favorable. Sensitive groups, including small children and pregnant people, should be especially careful when recreating in the river. Human Access Project warns the river remains dangerous for dogs, which can quickly fall ill or die from exposure. Recent rain and mild temperatures temporarily improved conditions, but upcoming heat could allow blooms to redevelop.
Update August 19, 2025: The Oregon Health Authority lifted its advisory warning of a harmful algal bloom on the Willamette River, stating "water monitoring has confirmed that the level of cyanotoxins in Ross Island Lagoon and the Willamette River...are below recreational guideline values for people." OHA continues to advise people be "alert to signs of cyanobacteria blooms...[which] can develop and disappear on any water body at any time when bloom conditions are favorable."
The change in river conditions comes after an unseasonably impressive rainstorm last weekend, which was followed by a few days of mild temperatures. Algal blooms thrive in hot weather, and the Portland area is set to heat up considerably over the next few days, so it's possible the river conditions could change yet again. As stated in a Human Access Project social media post: "Get it while you can and never take the ability to swim in our river for granted."
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