Lake Natoma: toxic algae advisories
Lake Natoma, Sacramento County. See all Sacramento County waters.
What the state's records say
General awareness, last posted Nov 18, 2022. 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: 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 Natoma
The state has an advisory on file for Lake Natoma (General awareness), last posted Nov 18, 2022, 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 Lake Natoma 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 |
|---|---|
| Jedediah Smith Memorial Trail bridge | Reports on file, with no advisory level the state has classified. |
| Mississippi Bar | The state's latest record, from Jul 25, 2024, recommends no advisory. |
| at Black Miners Bar Boat Dock | General awareness, last posted Nov 18, 2022. No all-clear recorded. |
| Rainbow Bridge | The state's latest record, from Oct 11, 2022, recommends no advisory. |
| Lake Natoma Inn | The state's latest record, from Oct 11, 2022, recommends no advisory. |
| at Black Miners Bar Boat Dock | Algal mat general awareness sign, last posted Apr 22, 2022. No all-clear recorded. |
| Willow Creek in Lake Natoma | The state's latest record, from Sep 18, 2019, recommends no advisory. |
Advisory history
Every advisory record the state has published for Lake Natoma, 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 |
|---|---|---|---|
| Aug 19, 2024 | Jedediah Smith Memorial Trail bridge | NA - refer to Report Details | Under investigation |
| Jul 25, 2024 | Mississippi Bar | None | Updates from routine monitoring program-organization |
| Nov 2, 2023 | Mississippi Bar | None | Updates from routine monitoring program-organization |
| Oct 10, 2023 | Mississippi Bar | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 1, 2023 | Mississippi Bar | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 21, 2023 | Mississippi Bar | None | Updates from routine monitoring program-organization |
| Nov 18, 2022 | Mississippi Bar | General awareness | Rec general awareness |
| Nov 18, 2022 | at Black Miners Bar Boat Dock | General awareness | Rec general awareness |
| Nov 4, 2022 | at Black Miners Bar Boat Dock | General awareness | Rec general awareness |
| Nov 4, 2022 | Mississippi Bar | General awareness | Rec general awareness |
| Oct 19, 2022 | Mississippi Bar | General awareness | Rec general awareness |
| Oct 19, 2022 | at Black Miners Bar Boat Dock | General awareness | Rec general awareness |
| Oct 11, 2022 | Rainbow Bridge | None | Advisory based on visual and toxins |
| Oct 11, 2022 | Lake Natoma Inn | None | Advisory based on visual and toxins |
| Oct 6, 2022 | at Black Miners Bar Boat Dock | Caution | Floating/planktonic bloom observed; Suspected bloom, investigation ongoing |
| Apr 22, 2022 | at Black Miners Bar Boat Dock | Algal mat alert sign | Bottom/benthic bloom observed |
| Apr 22, 2022 | at Black Miners Bar Boat Dock | Algal mat general awareness sign | Bottom/benthic bloom observed |
| Sep 18, 2019 | Willow Creek in Lake Natoma | None |
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.