Big Bear Lake: toxic algae advisories
Big Bear Lake, Riverside County. See all Riverside County waters.
What the state's records say
Danger advisory, last posted Aug 28, 2024. 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 Big Bear Lake
The state has an advisory on file for Big Bear Lake (Danger advisory), last posted Aug 28, 2024, 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 Oct 17, 2026: about 940,000 cells/mL of cyanobacteria near the center of Big Bear Lake.
A satellite estimate from EPA CyAN for a 10.9 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Oct 17, 2026 | about 940,000 cells/mL |
| Oct 10, 2026 | about 2,600,000 cells/mL |
| Oct 3, 2026 | about 2,600,000 cells/mL |
| Sep 26, 2026 | about 2,500,000 cells/mL |
| Sep 19, 2026 | about 2,000,000 cells/mL |
| Sep 12, 2026 | about 2,500,000 cells/mL |
| Sep 5, 2026 | about 1,600,000 cells/mL |
| Aug 29, 2026 | about 1,900,000 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 |
|---|---|
| Boulder Bay south east end of cove | Danger advisory, last posted Aug 28, 2024. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Big Bear 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 |
|---|---|---|---|
| Aug 28, 2024 | Boulder Bay south east end of cove | Danger | Alert-high concentration toxins |
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.