Klamath River: toxic algae advisories
Klamath River, Del Norte County. See all Del Norte County waters.
What the state's records say
Warning advisory, last posted Sep 18, 2026. No all-clear recorded.
4 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: Toxins may be at levels that can harm people and animals. Do not swim or let children or pets in the water, and stay away from scum.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Klamath River
The state has an advisory on file for Klamath River (Warning advisory), last posted Sep 18, 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 |
|---|---|
| Estuary (RM 0.5) | Reports on file, with no advisory level the state has classified. |
| at South Slough (RM 0.1) | Reports on file, with no advisory level the state has classified. |
| near Klamath (RM 6.0) | Reports on file, with no advisory level the state has classified. |
| Campground Sandy Boat Ramp (R-1) | Caution advisory, last posted Sep 18, 2026. No all-clear recorded. |
| at Klamath Glen (Roy Rook) | Reports on file, with no advisory level the state has classified. |
| near Klamath (RM 6.0) | Reports on file, with no advisory level the state has classified. |
| at South Slough RM 0.1 | Reports on file, with no advisory level the state has classified. |
| Estuary (RM 0.5) | Reports on file, with no advisory level the state has classified. |
| near Klamath RM 6.0 | The state's latest record, from Jul 20, 2021, recommends no advisory. |
| at South Slough RM 0.1 | The state's latest record, from Jul 20, 2021, recommends no advisory. |
| Klamath River near Klamath RM 6.0 | Warning advisory, last posted Oct 19, 2020. No all-clear recorded. |
| Klamath River Estuary RM 0.5 | Caution advisory, last posted Oct 19, 2020. No all-clear recorded. |
| Klamath River at South Slough RM 0.1 | Caution advisory, last posted Oct 19, 2020. No all-clear recorded. |
| Klamath River Estuary | Reports on file, with no advisory level the state has classified. |
| Klamath River at South Slough | Reports on file, with no advisory level the state has classified. |
Advisory history
Every advisory record the state has published for Klamath 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 9, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 25, 2026 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 25, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 25, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 24, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 18, 2026 | Campground Sandy Boat Ramp (R-1) | Caution | Updates from routine monitoring program-organization |
| Sep 16, 2026 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 16, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 16, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 11, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 13, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 5, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 5, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 5, 2026 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2026 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 13, 2026 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 13, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 13, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 8, 2026 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 8, 2026 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 8, 2026 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Dec 4, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Dec 4, 2025 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Dec 4, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 1, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 1, 2025 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 1, 2025 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 3, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 3, 2025 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 3, 2025 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 20, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 20, 2025 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 20, 2025 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 29, 2025 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 29, 2025 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 17, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 17, 2025 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 17, 2025 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 17, 2025 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 25, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 25, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 25, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 17, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 17, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 17, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 3, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 3, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 3, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 9, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 9, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 9, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 5, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 5, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 5, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 16, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 16, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 16, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 12, 2024 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 12, 2024 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 12, 2024 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 20, 2023 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Nov 20, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Nov 20, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Nov 3, 2023 | at Klamath Glen (Roy Rook) | NA - refer to Report Details | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Oct 6, 2023 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 6, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 6, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 18, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 18, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 31, 2023 | at Klamath Glen (Roy Rook) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 18, 2023 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 18, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 18, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2023 | Estuary (RM 0.5) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 18, 2023 | Estuary (RM 0.5) | Blank in the state's file | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 18, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 18, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2023 | Estuary (RM 0.5) | Blank in the state's file | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 13, 2023 | Estuary (RM 0.5) | Blank in the state's file | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 13, 2023 | at South Slough (RM 0.1) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 13, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 26, 2023 | Estuary (RM 0.5) | Blank in the state's file | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 26, 2023 | near Klamath (RM 6.0) | NA - refer to Report Details | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Nov 10, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | End date recorded: Dec 16, 2022. Updates from routine monitoring program-organization |
| Nov 10, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | End date recorded: Dec 16, 2022. Updates from routine monitoring program-organization |
| Nov 10, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | End date recorded: Dec 16, 2022. Updates from routine monitoring program-organization |
| Nov 10, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Nov 10, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Nov 10, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 20, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 20, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 6, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 6, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Oct 6, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 28, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 28, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 28, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 7, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 7, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Sep 7, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 18, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 18, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 18, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 4, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 4, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 1, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 1, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 1, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Aug 1, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 1, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 1, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 1, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jun 13, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jun 13, 2022 | at South Slough RM 0.1 | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jun 13, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jun 3, 2022 | Estuary (RM 0.5) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jun 3, 2022 | near Klamath (RM 6.0) | NA - refer to Report Details | Updates from routine monitoring program-organization |
| Jul 20, 2021 | near Klamath RM 6.0 | None | Updates from routine monitoring program-organization |
| Jul 20, 2021 | at South Slough RM 0.1 | None | Updates from routine monitoring program-organization |
| Oct 19, 2020 | Klamath River near Klamath RM 6.0 | Warning | Advisory based on visual and toxins |
| Oct 19, 2020 | Klamath River Estuary RM 0.5 | Caution | Advisory based on visual and toxins |
| Oct 19, 2020 | Klamath River at South Slough RM 0.1 | Caution | Advisory based on visual and toxins |
| Sep 29, 2018 | Klamath River Estuary | NA - refer to Report Details | |
| Sep 29, 2018 | Klamath River at South Slough | NA - refer to Report Details |
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.