Mormon Slough: toxic algae advisories
Mormon Slough, San Joaquin County. See all San Joaquin County waters.
What the state's records say
Danger advisory, last posted Aug 25, 2020. No all-clear recorded.
2 reported spots here have an advisory with 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 Mormon Slough
The state has an advisory on file for Mormon Slough (Danger advisory), last posted Aug 25, 2020, 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 W. Weber Ave. (MS) | The state's latest record, from Oct 1, 2026, recommends no advisory. |
| Moreli Boat Ramp | The state's latest record, from Oct 18, 2021, recommends no advisory. |
| Mormon Slough at Weber Avenue | Danger advisory, last posted Aug 25, 2020. No all-clear recorded. |
| Mormon Slough at Weber Avenue | Caution advisory, last posted Aug 27, 2019. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Mormon Slough, 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 |
|---|---|---|---|
| Oct 1, 2026 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 2, 2026 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 30, 2026 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 2, 2026 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 11, 2026 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 20, 2026 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 2, 2025 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 3, 2025 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 7, 2025 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 24, 2025 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 2, 2025 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 5, 2025 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 25, 2024 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 23, 2024 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 26, 2024 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 20, 2024 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 16, 2024 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 29, 2023 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 24, 2023 | near W. Weber Ave. (MS) | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 21, 2023 | near W. Weber Ave. (MS) | None | Updates from routine monitoring program-organization |
| Jun 16, 2023 | near W. Weber Ave. (MS) | None | Updates from routine monitoring program-organization |
| Sep 27, 2022 | near W. Weber Ave. (MS) | Caution | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Sep 15, 2022 | near W. Weber Ave. (MS) | Warning | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Sep 13, 2022 | near W. Weber Ave. (MS) | Caution | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Aug 26, 2022 | near W. Weber Ave. (MS) | Warning | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Aug 24, 2022 | near W. Weber Ave. (MS) | Warning | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Aug 17, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Aug 9, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jul 29, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jul 25, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jul 15, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jul 12, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jul 1, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jun 17, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Jun 10, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| May 27, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| May 19, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| May 12, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| May 2, 2022 | near W. Weber Ave. (MS) | Caution | Updates from routine monitoring program-organization |
| Oct 18, 2021 | Moreli Boat Ramp | None | Testing results below posting triggers |
| Aug 25, 2020 | Mormon Slough at Weber Avenue | Danger | Advisory based on visual and toxins |
| Aug 27, 2019 | Mormon Slough at Weber Avenue | Caution |
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.