Lake Mendocino: toxic algae advisories
Lake Mendocino, Mendocino County. See all Mendocino County waters.
What the state's records say
General awareness, last posted Jul 3, 2025. No all-clear recorded.
Reporting is voluntary, so the state may not have recorded an end even if conditions changed. Check posted signs and the official map.
What this level asks: The state recorded an advisory of a type outside the Caution, Warning and Danger levels. Read the sign posted at the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Lake Mendocino
The state has an advisory on file for Lake Mendocino (General awareness), last posted Jul 3, 2025, and no all-clear recorded. Keep your dog out of the water and away from scum on the shore until the state records an end.
Satellite estimate (not an advisory)
Week ending Aug 9, 2025: about 22,000 cells/mL of cyanobacteria near the center of Lake Mendocino.
A satellite estimate from EPA CyAN for a 6.3 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Aug 9, 2025 | about 22,000 cells/mL |
| Aug 2, 2025 | about 18,000 cells/mL |
| Jul 8, 2023 | about 9,000 cells/mL |
| Oct 30, 2021 | about 33,000 cells/mL |
| Sep 25, 2021 | about 42,000 cells/mL |
| Sep 18, 2021 | about 140,000 cells/mL |
| Sep 4, 2021 | about 80,000 cells/mL |
| Aug 21, 2021 | about 150,000 cells/mL |
This is a satellite estimate from the U.S. EPA's Cyanobacteria Assessment Network, not an advisory. It estimates how much cyanobacteria is in the water near the lake's center, not whether toxins are present: a high number does not mean toxins, and a low one does not mean there are none. It covers lakes of about 1 square kilometer and larger, so small ponds, dog parks and most rivers are not covered, and clouds can hide a lake for weeks. It never changes the advisory status above.
Satellite estimates: U.S. EPA Cyanobacteria Assessment Network (CyAN), from Copernicus Sentinel-3 data. Provisional, research-level estimates; EPA does not endorse this site. Checked Oct 22, 2026.
Reported spots
The state records each report at a spot, such as a beach or a boat ramp. Each spot's latest deciding record:
| Spot | Status |
|---|---|
| at South Ramp | The state's latest record, from Oct 16, 2026, recommends no advisory. |
| Miti Campground | General awareness, last posted Jul 3, 2025. No all-clear recorded. |
| South Boat Ramp | The state's latest record, from Jun 23, 2023, recommends no advisory. |
Advisory history
Every advisory record the state has published for Lake Mendocino, newest first. "None" is the state's record that no advisory was recommended on that date. "NA" records do not change a status.
| Date | Spot | State's level | Notes |
|---|---|---|---|
| Oct 16, 2026 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers |
| Aug 31, 2026 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers |
| Jun 26, 2026 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers |
| May 18, 2026 | at South Ramp | Caution | Advisory based on visual and toxins |
| May 18, 2026 | at South Ramp | Caution | Advisory based on visual and toxins |
| Oct 22, 2025 | at South Ramp | General awareness | No cyano bloom w/testing; Rec general awareness; Testing results below posting triggers |
| Aug 27, 2025 | at South Ramp | Caution | Lake-wide advisory |
| Jul 3, 2025 | at South Ramp | General awareness | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 3, 2025 | Miti Campground | General awareness | No cyano bloom w/testing; Testing results below posting triggers |
| Jul 3, 2025 | Miti Campground | General awareness | No cyano bloom w/testing; Testing results below posting triggers |
| Jun 26, 2025 | Miti Campground | NA - refer to Report Details | Under investigation |
| Oct 25, 2024 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 28, 2024 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 26, 2024 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 19, 2023 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers |
| Aug 28, 2023 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers |
| Aug 28, 2023 | at South Ramp | None | No cyano bloom w/testing; Testing results below posting triggers |
| Jun 23, 2023 | South Boat Ramp | None | End date recorded: Oct 12, 2022. No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 12, 2022 | South Boat Ramp | None | End date recorded: Oct 12, 2022. No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 12, 2022 | South Boat Ramp | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 14, 2022 | South Boat Ramp | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 29, 2022 | South Boat Ramp | None | No cyano bloom w/testing |
| May 25, 2022 | South Boat Ramp | None | No cyano bloom w/testing |
| May 25, 2022 | South Boat Ramp | None | No cyano bloom w/testing |
Source
Advisory data: California State Water Resources Control Board, Freshwater Harmful Algal Bloom Program, via data.ca.gov (public domain). Advisories are recommendations; reporting is voluntary and incomplete. The state's data. An advisory ends only when the state records a later "None" (no advisory recommended) at the same spot, or an end date. A blank end date is unknown.