Is the lake safe?

California

California algae bloom map

7 California lakes and rivers have a toxic algae report in the last 30 days, out of 318 with a full bloom history. Data checked 24 October 2026.

Danger advisory, last 30 daysWarning advisory, last 30 daysCaution advisory, last 30 daysBloom reported, last 30 daysNo report in the last 30 days Bigger dots have more years with blooms.

Lakes with a report in the last 30 days

Newest first. Reports older than 30 days are shown as no recent report.

How to read this map

Each dot is a lake or river with enough reports for its own page, placed at the centre of its reports. The colour shows the latest entry in California's official data, and bigger dots have had blooms in more years. California publishes reports every day, so this map is rebuilt daily.

Lakes without a dot may never have been tested. No report doesn't mean the water is safe. For official live conditions, see the California HABs Portal map, and browse every county on the California page.