California
Toxic algae in Siskiyou County lakes
28 lakes and waterways in Siskiyou County have harmful algal bloom reports in California's official data. The most recent entry is for Klamath River: There are no bloom reports for Klamath River in the last 30 days of California's data. The most recent was a bloom report on 4 August 2026 at below Indian Creek. Klamath River, Salmon River and Lake Shastina 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.
- Klamath River Bloom reported
- Salmon River Awareness sign
- Lake Shastina Bloom reported
- Butte Creek Bloom reported
- Tule Lake Wildlife Refuge Danger
- Scott River Awareness sign
- Copco Reservoir Bloom reported
- Iron Gate Reservoir Bloom reported
- J.C. Boyle Reservoir Bloom reported
- Lake Siskiyou Bloom reported
- Iron Creek Bloom reported
- Tule Lake Hydrologic Subarea 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.
- Applegate River 2026
- Burney Valley Creek 2025
- Calf Creek 2026
- Cherry Creek 2022
- Dillon Creek 2021
- Indian Creek 2021
- Kidder Creek 2026
- Moosehead Creek 2023
- Muskgrave Creek 2026
- Seiad Creek 2021
- Shasta River 2022
- South Fork Salmon River 2024
- St Claire Creek 2022
- Tule Lake 2025
- Walker Creek 2021
- Wooley Creek 2025
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.