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 San Diego River: There are no bloom reports for San Diego River in the last 30 days of California's data. The most recent was a bloom report on 19 June 2026 at San Diego River, Sefton Park. 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.
- San Diego River Bloom reported
- San Luis Rey River Bloom reported
- Whelan Lake Caution
- Mission Bay Bloom reported
- Cedar Creek Bloom reported
- Kumeyaay Lake Bloom reported
- Chollas Creek Bloom reported
- Sweetwater River Bloom reported
- Lindo Lake Danger
- Morena Reservoir Bloom reported
- Santa Margarita River Bloom reported
- Lake San Marcos Warning
- Agua Caliente Creek Bloom reported
- Pine Valley Creek Bloom reported
- San Dieguito River Awareness sign
- Lake Henshaw Bloom reported
- Lake Hodges Bloom reported
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.
- Agua Hedionda Creek 2023
- Agua Hedionda Lagoon 2020
- Big Laguna Lake 2022
- Black Mountain Creek 2023
- Boulder Creek 2023
- Calaveras Reservoir 2017
- Cedar Creek Falls 2026
- Chollas Lake 2022
- Cold Stream 2023
- Cuyamaca Reservoir 2022
- Doane Creek 2023
- Eagle Scout Lake 2026
- Escondido Creek 2022
- Espinosa Creek 2023
- Famosa Slough And Channel 2026
- Guajome Lake 2024
- Harper Creek 2023
- Japacha Creek 2023
- Juaquapin Creek 2023
- Kit Carson Park Eagle Scout Lake 2026
- Kitchen Creek 2024
- Lake Barrett 2020
- Lake O'Neill 2026
- Lake Samagatuma 2026
- Libby Lake 2024
- Los Jilgueros Preserve Ponds 2024
- Los Penasquitos Creek 2021
- Los Rasales Lake 2022
- Lower Otay Reservoir 2023
- Miramar Reservoir 2026
- Moosa Canyon Pond 2025
- Oceanside Harbor 2022
- Otay River 2024
- Private Lake 2026
- Private Pond 2026
- San Felipe Creek 2023
- San Onofre Creek 2022
- San Vicente Reservoir 2023
- Santee Lakes 2024
- Santee Lakes #5 2025
- Stonewall Creek 2023
- Tree Lake 2026
- Viejas Creek Spring Pond 2023
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.