Napa River: toxic algae advisories
Napa River, Napa County. See all Napa County waters.
What the state's records say
The state's latest record, from Sep 2, 2026, recommends no advisory.
Last advisory on file: Aug 28, 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 Napa River
The state's latest record, from Sep 2, 2026, recommends no advisory. For Napa River, 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 |
|---|---|
| Napa River ecology reserve by Yountville Cross Rd | The state's latest record, from Sep 2, 2026, recommends no advisory. |
| Napa River at Zinfandel Lane | The state's latest record, from Sep 2, 2026, recommends no advisory. |
| Napa River at Yountville Ecopreserve | The state's latest record, from Jun 30, 2025, recommends no advisory. |
Advisory history
Every advisory record the state has published for Napa River, 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 2, 2026 | Napa River ecology reserve by Yountville Cross Rd | None | Testing results below posting triggers |
| Sep 2, 2026 | Napa River at Zinfandel Lane | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jul 1, 2026 | Napa River ecology reserve by Yountville Cross Rd | None | No cyano, other algae present. |
| Jul 1, 2026 | Napa River at Zinfandel Lane | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2025 | Napa River at Zinfandel Lane | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 30, 2025 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| Jun 30, 2025 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| Jun 30, 2025 | Napa River at Zinfandel Lane | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 28, 2024 | Napa River ecology reserve by Yountville Cross Rd | None | No cyano, other algae present. |
| Aug 28, 2024 | Napa River at Zinfandel Lane | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Aug 28, 2024 | Napa River ecology reserve by Yountville Cross Rd | Algal mat general awareness sign | |
| Jun 27, 2024 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| Jun 27, 2024 | Napa River at Zinfandel Lane | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 29, 2023 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| May 18, 2023 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| Aug 30, 2022 | Napa River at Yountville Ecopreserve | None | End date recorded: Dec 31, 2022. No cyano bloom w/testing |
| Aug 30, 2022 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| Jun 29, 2022 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
| May 20, 2022 | Napa River at Yountville Ecopreserve | None | No cyano bloom w/testing |
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.