Trinity River: toxic algae advisories
Trinity River, Humboldt County. See all Humboldt County waters.
What the state's records say
Caution advisory, last posted Oct 19, 2026. No all-clear recorded.
3 reported spots here have an advisory with 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 Trinity River
The state has an advisory on file for Trinity River (Caution advisory), last posted Oct 19, 2026, 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.
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 the Southern Boundary of Reservation | General awareness, last posted Oct 19, 2026. No all-clear recorded. |
| at Weitchpec | The state's latest record, from Aug 13, 2026, recommends no advisory. |
| at the Southern Boundary of Reservation | The state's latest record, from Nov 10, 2022, recommends no advisory. |
| near Klamath River | The state's latest record, from Nov 4, 2021, recommends no advisory. |
| at the southern boundary of reservation | The state's latest record, from Jul 20, 2021, recommends no advisory. |
| right past town of willow creek going east off highway; river access sign, pull out left side of the highway and trail down | Caution advisory, last posted Jul 15, 2021. No all-clear recorded. |
| Trinity River near Mouth | Caution advisory, last posted Oct 19, 2020. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Trinity River, 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 19, 2026 | at the Southern Boundary of Reservation | General awareness | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 9, 2026 | at Weitchpec | NA - refer to Report Details | Bottom/benthic bloom observed; Updates from routine monitoring program-organization |
| Oct 2, 2026 | at Weitchpec | NA - refer to Report Details | Bottom/benthic bloom observed; Updates from routine monitoring program-organization |
| Oct 1, 2026 | at the Southern Boundary of Reservation | Algal mat alert sign | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Sep 24, 2026 | at Weitchpec | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 17, 2026 | at the Southern Boundary of Reservation | Algal mat alert sign | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Sep 17, 2026 | at the Southern Boundary of Reservation | Algal mat alert sign | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Sep 10, 2026 | at the Southern Boundary of Reservation | Algal mat alert sign | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Sep 10, 2026 | at the Southern Boundary of Reservation | Algal mat alert sign | Advisory based on visual and toxins |
| Sep 2, 2026 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 19, 2026 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 13, 2026 | at Weitchpec | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2026 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2026 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2026 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 8, 2026 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 25, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 3, 2025 | at Weitchpec | Algal mat alert sign | Advisory based on visual and toxins; Bottom/benthic bloom observed |
| Oct 1, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 16, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 3, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 20, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 24, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 8, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 13, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 10, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 22, 2025 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 25, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 17, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 3, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 19, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 9, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 22, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 5, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 17, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 16, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 12, 2024 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 7, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 3, 2023 | at Weitchpec | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 6, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 18, 2023 | at Weitchpec | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 18, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 31, 2023 | at Weitchpec | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 29, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 18, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 18, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 28, 2023 | at Weitchpec | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 13, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 26, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 17, 2023 | at the Southern Boundary of Reservation | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 10, 2022 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 20, 2022 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 6, 2022 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 28, 2022 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 7, 2022 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 18, 2022 | at the Southern Boundary of Reservation | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 1, 2022 | at the Southern Boundary of Reservation | None | Updates from routine monitoring program-organization |
| Jul 25, 2022 | at the Southern Boundary of Reservation | None | Updates from routine monitoring program-organization |
| Jul 1, 2022 | at the Southern Boundary of Reservation | None | Updates from routine monitoring program-organization |
| Jun 17, 2022 | at the Southern Boundary of Reservation | None | Updates from routine monitoring program-organization |
| Jun 3, 2022 | at the Southern Boundary of Reservation | None | Updates from routine monitoring program-organization |
| Nov 4, 2021 | near Klamath River | None | Testing results below posting triggers |
| Jul 20, 2021 | at the southern boundary of reservation | None | Testing results below posting triggers |
| Jul 15, 2021 | right past town of willow creek going east off highway; river access sign, pull out left side of the highway and trail down | Caution | Advisory based on visual and toxins |
| Oct 19, 2020 | Trinity River near Mouth | 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.