Checked October 19, 2026 · Sources: California State Water Resources Control Board and regional water boards, Centers for Disease Control and Prevention (CDC)
California’s water boards issued a run of toxic algae advisories in late August and early September, from Big Bear Lake to the Eastern Sierra and the North Coast rivers. These advisories stay in effect “until further notice,” so if you’re planning a fall camping or hiking trip with your dog, check the lake before you go. Dogs are the most likely to get sick, because they swim through the water, drink it and lick it off their fur.
Advisories issued this season
| Waterbody | County | Issued | Level | Where |
|---|---|---|---|---|
| Big Bear Lake | San Bernardino | Aug. 27 | Warning | Throughout the lake; signs posted around it |
| H.V. Eastman Lake | Madera | Aug. 27 | Danger | Shoreline scum near the east and west boat ramps |
| Crowley Lake | Mono | Aug. 28 | Danger / Caution | Danger at Hilton Creek drainage; Caution at South Landing Marina |
| Bridgeport Reservoir | Mono | Sept. 3 | Danger / Caution | Danger at the old marina boat ramp and dam areas; Caution at the RV park |
| Lake Hemet | Riverside | Sept. 3 | Warning | Lake-wide; follow posted signs |
| North Coast rivers | Humboldt, Mendocino, Sonoma, Trinity and others | Aug. 26 | “Toxic Algae Alert” signs where mats were found | Monitoring on the Klamath, Trinity, Salmon, Scott, Mad, Eel, South Fork Eel, Van Duzen, Navarro and Russian rivers |
Advisory levels and locations change as wind and waves move a bloom, and a lake can be posted or cleared after this list was checked. For the latest status, use the state’s HAB Reports Web Map before you go, and follow any signs at the shore, even if a lake isn’t on this list.
What the advisories tell dog owners
- Don’t let your dog swim in or drink the water, or eat algae or scum along the shore.
- In “Danger” areas, keep dogs out of the water and away from the shoreline scum entirely.
- Stay away from water that looks cloudy, discolored or scummy, even where there’s no sign.
- If your dog does go in, rinse them with clean water right away and don’t let them lick their coat.
- Boiling or filtering doesn’t make bloom water safe, so bring drinking water for your dog.
Signs your dog needs a vet now
The CDC warns that animals can become seriously ill or die within hours of contact with toxic algae. If your dog shows signs such as vomiting, drooling, weakness or wobbling, trouble breathing, shaking or a seizure after being in or near water, go to a veterinarian immediately and tell them about the possible exposure. Don’t wait to see if it passes.
You can also call the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661 (both charge a fee).
Report a bloom
If you see a suspicious bloom or your dog gets sick after water contact, report it to California’s harmful algal bloom program: the HABs hotline at 1-844-729-6466 (toll free), email CyanoHAB.Reports@waterboards.ca.gov, or the online bloom report form on the California HABs Portal.
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This article is general information for dog owners, not veterinary or legal advice. Advisories can be issued or lifted at any time. Follow the official source when it differs from this article.
Sources
- Big Bear Lake: Warning advisory, Aug. 27, 2026
- H.V. Eastman Lake: Danger advisory, Aug. 27, 2026
- Crowley Lake: Advisory, Aug. 28, 2026
- Bridgeport Reservoir: Advisory, Sept. 3, 2026
- Lake Hemet: Warning advisory, Sept. 3, 2026
- North Coast: North Coast Water Board release, Aug. 26, 2026
- State Water Board: Freshwater CyanoHABs Program; HAB Reports Web Map
- CDC: About harmful algal blooms; Preventing pet and livestock illnesses