San Juan Creek: toxic algae advisories
San Juan Creek, Orange County. See all Orange County waters.
What the state's records say
Algal mat alert sign, last posted Sep 1, 2026. 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 San Juan Creek
The state has an advisory on file for San Juan Creek (Algal mat alert sign), last posted Sep 1, 2026, 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.
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 |
|---|---|
| Near horse trail | Algal mat alert sign, last posted Sep 1, 2026. No all-clear recorded. |
| Outfall to Ocean, interface of San Juan Creek, between Lifeguard Towers 9 and 10 | The state's latest record, from Nov 20, 2023, recommends no advisory. |
Advisory history
Every advisory record the state has published for San Juan Creek, 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 1, 2026 | Near horse trail | Algal mat alert sign | |
| Nov 20, 2023 | Outfall to Ocean, interface of San Juan Creek, between Lifeguard Towers 9 and 10 | None | No cyano bloom w/photos |
| Nov 3, 2023 | Outfall to Ocean, interface of San Juan Creek, between Lifeguard Towers 9 and 10 | Visual observation | Under investigation; Visual monitoring only-present bloom |
| Nov 3, 2023 | Outfall to Ocean, interface of San Juan Creek, between Lifeguard Towers 9 and 10 | NA - refer to Report Details | Under investigation |
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.