Lake Shastina: toxic algae advisories
Lake Shastina, Siskiyou County. See all Siskiyou County waters.
What the state's records say
Danger advisory, last posted May 14, 2025. 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 seriously harm people and animals. Stay out of the water and keep children and pets away from the water and the shore.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Lake Shastina
The state has an advisory on file for Lake Shastina (Danger advisory), last posted May 14, 2025, 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 Sep 19, 2026: about 110,000 cells/mL of cyanobacteria near the center of Lake Shastina.
A satellite estimate from EPA CyAN for a 2.2 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Sep 19, 2026 | about 110,000 cells/mL |
| Sep 12, 2026 | about 2,700,000 cells/mL |
| Sep 5, 2026 | about 1,300,000 cells/mL |
| Aug 29, 2026 | about 2,000,000 cells/mL |
| Aug 22, 2026 | about 1,900,000 cells/mL |
| Aug 15, 2026 | about 1,100,000 cells/mL |
| Aug 8, 2026 | about 960,000 cells/mL |
| Jun 6, 2026 | about 4,200,000 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 |
|---|---|
| Boat Ramp at Juniper Peak Rd | The state's latest record, from Jun 25, 2026, recommends no advisory. |
| Dwinnell Way | Danger advisory, last posted May 14, 2025. No all-clear recorded. |
| lake-wide | The state's latest record, from Apr 25, 2022, recommends no advisory. |
| Spot not described | The state's latest record, from May 21, 2021, recommends no advisory. |
Advisory history
Every advisory record the state has published for Lake Shastina, 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 |
|---|---|---|---|
| Jun 25, 2026 | Boat Ramp at Juniper Peak Rd | None | No cyano bloom w/photos; Visual monitoring only-absent bloom |
| Jun 5, 2026 | Boat Ramp at Juniper Peak Rd | Caution | Suspected bloom, investigation ongoing |
| May 22, 2026 | Boat Ramp at Juniper Peak Rd | Visual observation | Suspected bloom, investigation ongoing |
| May 22, 2026 | Boat Ramp at Juniper Peak Rd | Visual observation | Suspected bloom, investigation ongoing |
| May 14, 2025 | Dwinnell Way | Danger | Advisory based on visual and toxins; Alert-high concentration toxins |
| May 14, 2025 | Dwinnell Way | Danger | Advisory based on visual and toxins |
| May 7, 2025 | Dwinnell Way | Caution | Visual monitoring only-present bloom |
| Jul 31, 2024 | Dwinnell Way | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| Jul 31, 2024 | Dwinnell Way | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| Apr 25, 2022 | lake-wide | None | End date recorded: Apr 25, 2022. visual monitoring based advisory |
| Apr 25, 2022 | lake-wide | None | visual monitoring based advisory |
| Apr 25, 2022 | lake-wide | Blank in the state's file | visual monitoring based advisory |
| May 21, 2021 | Spot not described | None | Testing results below posting triggers |
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.