Toxic algae advisories at California and Missouri lakes and rivers

Which waters have a harmful algal bloom advisory on file with the state, when it was posted, and whether the state has recorded an end. For anyone heading to the water: swimmers, families, paddlers, anglers and dog owners.

California: the state's file dated Oct 20, 2026, newest record Oct 20, 2026. Missouri: read Oct 22, 2026, newest record Oct 4, 2026. An advisory stays listed until the state records an end. A water that is not listed has no advisory on file, which is not the same as being free of algae.

Advisories posted in the last 30 days

See all 535 waters whose latest record is an advisory, including 491 older ones the state never recorded an end for.

Bringing a dog?

Dogs swim through scum and drink lake water, so algae affects them more than most people. How to read an advisory before a lake day with your dog.

Find a lake

1120 lakes and rivers, each with its own page and every state record on file:

• California, by county (records since 2016)
• Missouri (records since 2017)