Lake Ralphine: toxic algae advisories
Lake Ralphine, Sonoma County. See all Sonoma County waters.
What the state's records say
Warning advisory, last posted Jul 20, 2026. 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 harm people and animals. Do not swim or let children or pets in the water, and stay away from scum.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Lake Ralphine
The state has an advisory on file for Lake Ralphine (Warning advisory), last posted Jul 20, 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 |
|---|---|
| Howarth Park | Caution advisory, last posted Jul 20, 2026. No all-clear recorded. |
| Howarth Park | The state's latest record, from Nov 15, 2022, recommends no advisory. |
| Lake Ralphine, Howarth Park | Warning advisory, last posted Aug 31, 2020. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Lake Ralphine, 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 |
|---|---|---|---|
| Jul 20, 2026 | Howarth Park | Caution | visual monitoring based advisory |
| May 27, 2026 | Howarth Park | Caution | visual monitoring based advisory |
| May 27, 2026 | Howarth Park | Caution | Updates from routine monitoring program-organization |
| Jan 21, 2026 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; Updates from routine monitoring program-organization; visual monitoring based advisory; Visual monitoring only-present bloom |
| Jan 5, 2026 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; Visual monitoring only-present bloom |
| Jul 14, 2025 | Howarth Park | Caution | Bottom/benthic bloom observed; Floating/planktonic bloom observed; Lake-wide advisory; Visual monitoring only-present bloom |
| Jun 28, 2024 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| May 29, 2024 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| Jun 29, 2023 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| Jun 29, 2023 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| Jun 22, 2023 | Howarth Park | Caution | Floating/planktonic bloom observed; Lake-wide advisory; visual monitoring based advisory; Visual monitoring only-present bloom |
| Nov 15, 2022 | Howarth Park | None | End date recorded: Nov 15, 2022. De-posting advisory. |
| Nov 15, 2022 | Howarth Park | None | De-posting advisory. |
| Aug 9, 2022 | Howarth Park | Caution | Updates from routine monitoring program-organization |
| Aug 4, 2022 | Howarth Park | None | Updates from routine monitoring program-organization |
| Jul 13, 2022 | Howarth Park | None | Updates from routine monitoring program-organization |
| Jul 6, 2022 | Howarth Park | Caution | Updates from routine monitoring program-organization |
| Jun 30, 2022 | Howarth Park | None | Updates from routine monitoring program-organization |
| Jun 1, 2022 | Howarth Park | None | De-posting advisory. |
| May 20, 2022 | Howarth Park | Caution | visual monitoring based advisory |
| Aug 31, 2020 | Lake Ralphine, Howarth Park | Warning | Advisory based on visual and toxins |
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.