Is the lake safe?

California

Toxic algae in San Diego County lakes

60 lakes and waterways in San Diego County have harmful algal bloom reports in California's official data. The most recent entry is for Miramar Reservoir: There are no bloom reports for Miramar Reservoir in the last 30 days of California's data. The most recent was a Caution advisory on 22 September 2026 at Miramar Reservoir. San Diego River, Whelan Lake and Mission Bay and 5 more have had blooms in three or more years.

Lakes with bloom history

Newest report first. Each lake has its own page with the full history and what the results mean.

Other waterbodies with a report

These have one or two reports in a single year, which isn't enough history for a page of their own yet.

Source: California State Water Resources Control Board, official data, checked 24 October 2026. For today's conditions see the California HABs Portal map. No report doesn't mean a lake is safe: most water is only tested occasionally.