Castaic Lagoon: toxic algae advisories
Castaic Lagoon, Los Angeles County. See all Los Angeles County waters.
What the state's records say
The state's latest record, from Sep 17, 2026, recommends no advisory.
Last advisory on file: Jun 1, 2026.
That reflects what the state knew on that date. It is not a finding that the water is safe now: blooms can return within days, and many are never reported.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Castaic Lagoon
The state's latest record, from Sep 17, 2026, recommends no advisory. For Castaic Lagoon, that is not the same as an all-clear for today. Look at the water before your dog goes in: keep it out of green, blue-green or scummy water and away from mats on the shore.
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 |
|---|---|
| Lagoon Swim beach downstream of lake | The state's latest record, from Sep 17, 2026, recommends no advisory. |
Advisory history
Every advisory record the state has published for Castaic Lagoon, 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 17, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 24, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 11, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 28, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 28, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 15, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 8, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 30, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 23, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 23, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 9, 2026 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 1, 2026 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| May 4, 2026 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Mar 20, 2026 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Mar 6, 2026 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Feb 11, 2026 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Jan 22, 2026 | Lagoon Swim beach downstream of lake | Warning | Updates from routine monitoring program-organization |
| Jan 13, 2026 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Aug 25, 2025 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Aug 18, 2025 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Aug 14, 2025 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Aug 1, 2025 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Jul 25, 2025 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Jul 24, 2025 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 18, 2025 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 1, 2025 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 26, 2025 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 26, 2025 | Lagoon Swim beach downstream of lake | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 17, 2025 | Lagoon Swim beach downstream of lake | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 10, 2025 | Lagoon Swim beach downstream of lake | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 10, 2024 | Lagoon Swim beach downstream of lake | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| Sep 3, 2024 | Lagoon Swim beach downstream of lake | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 26, 2024 | Lagoon Swim beach downstream of lake | None | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 21, 2024 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Aug 13, 2024 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 30, 2024 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 25, 2024 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jul 8, 2024 | Lagoon Swim beach downstream of lake | Caution | Lake-wide advisory; Updates from routine monitoring program-organization |
| Jun 21, 2024 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 12, 2024 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| May 28, 2024 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Sep 14, 2023 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Sep 14, 2023 | Lagoon Swim beach downstream of lake | Caution | Updates from routine monitoring program-organization |
| Sep 14, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 9, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 8, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 28, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 6, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 5, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 23, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 15, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 7, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 2, 2023 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Sep 23, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Sep 16, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Sep 8, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 26, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 19, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 11, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Aug 3, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 27, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 13, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jul 7, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 21, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 20, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 16, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| Jun 3, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| May 23, 2022 | Lagoon Swim beach downstream of lake | None | Updates from routine monitoring program-organization |
| May 23, 2022 | Lagoon Swim beach downstream of lake | None | visual monitoring based advisory |
| May 23, 2022 | Lagoon Swim beach downstream of lake | None | 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.