Lewiston Lake: toxic algae advisories
Lewiston Lake, Trinity County. See all Trinity County waters.
What the state's records say
Caution advisory, last posted Jul 7, 2021. 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: Algae that can make toxins may be present. Keep people, children and pets away from algae and scum, and do not let pets drink the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Lewiston Lake
The state has an advisory on file for Lewiston Lake (Caution advisory), last posted Jul 7, 2021, 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)
No satellite reading on file for Lewiston Lake in recent weeks. Clouds, ice, or a lake shape the satellite's estimate near its center misses can cause this. It is a gap in the data, not a reading.
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 |
|---|---|
| Resort (106LRRSRT) | The state's latest record, from Sep 2, 2026, recommends no advisory. |
| Lakewide | The state's latest record, from Oct 28, 2022, recommends no advisory. |
| near Pine Cove | The state's latest record, from Jul 7, 2021, recommends no advisory. |
| Dam | Caution advisory, last posted Jul 7, 2021. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Lewiston Lake, 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 |
|---|---|---|---|
| Sep 2, 2026 | Resort (106LRRSRT) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 25, 2026 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers |
| Jun 25, 2026 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers |
| May 14, 2026 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers |
| Nov 6, 2025 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers |
| Aug 20, 2025 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 18, 2025 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 25, 2024 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 22, 2024 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 1, 2024 | Resort (106LRRSRT) | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Dec 31, 2023 | Resort (106LRRSRT) | None | End date recorded: Dec 31, 2023. De-posting advisory. |
| Oct 30, 2023 | Resort (106LRRSRT) | Algal mat alert sign | Advisory based on visual and toxins; Alert-detached mats observed |
| Aug 28, 2023 | Resort (106LRRSRT) | Algal mat alert sign | Advisory based on visual and toxins; Alert-detached mats observed; Alert-high concentration toxins; Updates from routine monitoring program-organization |
| Jul 5, 2023 | Resort (106LRRSRT) | Algal mat alert sign | Advisory based on visual and toxins; Alert-detached mats observed; Alert-high concentration toxins; Updates from routine monitoring program-organization |
| Oct 28, 2022 | Lakewide | None | End date recorded: Oct 28, 2022. Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 28, 2022 | Lakewide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 14, 2022 | Lakewide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 21, 2022 | Lakewide | None | Updates from routine monitoring program-organization |
| May 31, 2022 | Lakewide | None | Updates from routine monitoring program-organization |
| Jul 7, 2021 | near Pine Cove | None | Updates from routine monitoring program-organization |
| Jul 7, 2021 | Dam | Caution | Advisory based on visual and toxins |
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.