Clifton Court Forebay: toxic algae advisories
Clifton Court Forebay, Contra Costa County. See all Contra Costa County waters.
What the state's records say
The state's latest record, from Oct 19, 2026, recommends no advisory.
Last advisory on file: Sep 5, 2024.
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 Clifton Court Forebay
The state's latest record, from Oct 19, 2026, recommends no advisory. For Clifton Court Forebay, 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.
Satellite estimate (not an advisory)
Week ending Sep 5, 2026: about 12,000 cells/mL of cyanobacteria near the center of Clifton Court Forebay.
A satellite estimate from EPA CyAN for a 9.0 km² lake. It does not measure toxins and does not change the advisory status.
| Week ending | Estimate |
|---|---|
| Sep 5, 2026 | about 12,000 cells/mL |
| Jul 4, 2026 | about 1,900,000 cells/mL |
| Jun 27, 2026 | about 2,500,000 cells/mL |
| Jun 20, 2026 | about 1,500,000 cells/mL |
| Apr 27, 2024 | about 170,000 cells/mL |
| Nov 26, 2022 | about 29,000 cells/mL |
| Aug 27, 2022 | about 390,000 cells/mL |
| Aug 20, 2022 | about 620,000 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 |
|---|---|
| Inlet | The state's latest record, from Oct 19, 2026, recommends no advisory. |
| inlet | The state's latest record, from Jul 16, 2021, recommends no advisory. |
| Clifton Court Forebay inlet | The state's latest record, from Nov 2, 2020, recommends no advisory. |
Advisory history
Every advisory record the state has published for Clifton Court Forebay, 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 19, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 2, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 15, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 10, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 10, 2026 | Inlet | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 29, 2026 | Inlet | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 10, 2026 | Inlet | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 12, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 22, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 1, 2026 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 14, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 2, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 2, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 15, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 2, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Aug 18, 2025 | Inlet | None | Updates from routine monitoring program-organization |
| Jul 25, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 11, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 30, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 11, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| May 23, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Apr 25, 2025 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 25, 2024 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Sep 26, 2024 | Inlet | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Sep 20, 2024 | Inlet | None | Updates from routine monitoring program-organization |
| Sep 5, 2024 | Inlet | Caution | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| Aug 20, 2024 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jul 12, 2024 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 28, 2024 | Inlet | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 14, 2024 | Inlet | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| May 23, 2024 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Apr 25, 2024 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Oct 27, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| Oct 16, 2023 | Inlet | Algal mat general awareness sign | Updates from routine monitoring program-organization |
| Sep 29, 2023 | Inlet | Algal mat alert sign | Bottom/benthic bloom observed; Updates from routine monitoring program-organization |
| Sep 15, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| Aug 31, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| Aug 31, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| Aug 15, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| Jul 14, 2023 | Inlet | None | Updates from routine monitoring program-organization; Visual monitoring only-absent bloom |
| Jun 23, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| May 25, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| May 2, 2023 | Inlet | None | Updates from routine monitoring program-organization |
| Nov 1, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Oct 17, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Sep 30, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Sep 16, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Sep 8, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Aug 30, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Aug 24, 2022 | Inlet | Caution | Updates from routine monitoring program-organization |
| Aug 24, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Aug 18, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jul 29, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jul 15, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jun 27, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jun 27, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jun 14, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jun 1, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Apr 28, 2022 | Inlet | None | Updates from routine monitoring program-organization |
| Jul 16, 2021 | inlet | None | Testing results below posting triggers |
| Nov 2, 2020 | Clifton Court Forebay inlet | None | Testing results below posting triggers |
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.