Big Lagoon: toxic algae advisories
Big Lagoon, Humboldt County. See all Humboldt County waters.
What the state's records say
Warning advisory, last posted Oct 15, 2020. No all-clear recorded.
2 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 Big Lagoon
The state has an advisory on file for Big Lagoon (Warning advisory), last posted Oct 15, 2020, 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 23, 2025: about 11,000 cells/mL of cyanobacteria near the center of Big Lagoon.
A satellite estimate from EPA CyAN for a 5.8 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Aug 23, 2025 | about 11,000 cells/mL |
| Dec 24, 2022 | about 8,100 cells/mL |
| Nov 19, 2022 | about 120,000 cells/mL |
| Aug 27, 2022 | about 180,000 cells/mL |
| Dec 19, 2020 | about 33,000 cells/mL |
| Sep 5, 2020 | about 110,000 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 |
|---|---|
| Lagoonwide | The state's latest record, from Sep 29, 2026, recommends no advisory. |
| Lagoonwide | The state's latest record, from Oct 31, 2022, recommends no advisory. |
| Waterbody name submitted:Grizzly Creek Campground Redwoods State Park;Landmark submitted:None | The state's latest record, from Jun 29, 2021, recommends no advisory. |
| North | The state's latest record, from Jun 22, 2021, recommends no advisory. |
| Boat Ramp | The state's latest record, from Jun 22, 2021, recommends no advisory. |
| Big Lagoon | Warning advisory, last posted Oct 15, 2020. No all-clear recorded. |
| Big Lagoon - Campground | Caution advisory, last posted Aug 31, 2018. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Big Lagoon, 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 29, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 16, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 5, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 21, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 2, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 5, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 28, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 15, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 7, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Mar 19, 2026 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 24, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 8, 2025 | Lagoonwide | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 20, 2025 | Lagoonwide | Warning | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 13, 2025 | Lagoonwide | Danger | Advisory based on visual and toxins; Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 29, 2025 | Lagoonwide | Warning | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 17, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 8, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 24, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 10, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 28, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 12, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 1, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 17, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 7, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Mar 20, 2025 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 25, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 17, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 3, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 6, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 20, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 5, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 31, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 17, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 16, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 12, 2024 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Dec 31, 2023 | Lagoonwide | None | End date recorded: Dec 31, 2023. De-posting advisory. |
| Oct 19, 2023 | Lagoonwide | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 19, 2023 | Lagoonwide | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 2, 2023 | Lagoonwide | Caution | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 20, 2023 | Lagoonwide | Warning | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 20, 2023 | Lagoonwide | Warning | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 1, 2023 | Lagoonwide | Warning | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 1, 2023 | Lagoonwide | Warning | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 24, 2023 | Lagoonwide | Caution | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 18, 2023 | Lagoonwide | Caution | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 10, 2023 | Lagoonwide | Caution | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 8, 2023 | Lagoonwide | Caution | Advisory based on visual and toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 27, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 27, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 12, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 7, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 26, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 26, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 13, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 31, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 26, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 17, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 17, 2023 | Lagoonwide | None | No cyano bloom w/testing; Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 4, 2023 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 2, 2023 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 18, 2023 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 18, 2023 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 6, 2023 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Mar 20, 2023 | Lagoonwide | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 31, 2022 | Lagoonwide | None | End date recorded: Oct 24, 2022. Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 31, 2022 | Lagoonwide | None | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Oct 24, 2022 | Lagoonwide | None | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 30, 2022 | Lagoonwide | Caution | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 15, 2022 | Lagoonwide | Caution | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 15, 2022 | Lagoonwide | Danger | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 15, 2022 | Lagoonwide | Caution | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 15, 2022 | Lagoonwide | Danger | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 1, 2022 | Lagoonwide | Danger | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 1, 2022 | Lagoonwide | Danger | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 24, 2022 | Lagoonwide | Danger | Alert-high concentration toxins; Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 8, 2022 | Lagoonwide | Danger | Updates from routine monitoring program-organization |
| Jul 25, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| Jul 1, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| Jun 28, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| Jun 13, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| May 31, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| May 26, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| Apr 19, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| Apr 4, 2022 | Lagoonwide | None | Updates from routine monitoring program-organization |
| Jun 29, 2021 | Waterbody name submitted:Grizzly Creek Campground Redwoods State Park;Landmark submitted:None | None | Testing results below posting triggers |
| Jun 22, 2021 | North | None | Testing results below posting triggers |
| Jun 22, 2021 | Boat Ramp | None | Testing results below posting triggers |
| Oct 15, 2020 | Big Lagoon | Warning | Advisory based on visual and toxins |
| Aug 31, 2018 | Big Lagoon - Campground | Caution |
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.