Sherman Lake: toxic algae advisories
Sherman Lake, Sacramento County. See all Sacramento County waters.
What the state's records say
Caution advisory, last posted Sep 2, 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: 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 Sherman Lake
The state has an advisory on file for Sherman Lake (Caution advisory), last posted Sep 2, 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)
Week ending Aug 15, 2026: about 6,500 cells/mL of cyanobacteria near the center of Sherman Lake.
A satellite estimate from EPA CyAN for a 7.4 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Aug 15, 2026 | about 6,500 cells/mL |
| Jul 18, 2026 | about 9,600 cells/mL |
| Jan 24, 2026 | about 41,000 cells/mL |
| Feb 1, 2025 | about 68,000 cells/mL |
| Oct 19, 2024 | about 7,900 cells/mL |
| Sep 14, 2024 | about 7,700 cells/mL |
| Jul 13, 2024 | about 18,000 cells/mL |
| May 4, 2024 | about 17,000 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 |
|---|---|
| Sherman Island County Park Boat Ramp | Caution advisory, last posted Sep 2, 2022. No all-clear recorded. |
| Sherman Island Park at Boat Ramp | Caution advisory, last posted Jul 21, 2021. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Sherman 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, 2022 | Sherman Island County Park Boat Ramp | Caution | Advisory based on visual and toxins; Floating/planktonic bloom observed |
| Jul 21, 2021 | Sherman Island Park at Boat Ramp | Caution | visual monitoring based advisory |
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.