Is Lake Oroville safe? Toxic algae status
Butte County, California. Harmful algal bloom (blue-green algae) reports from the California State Water Resources Control Board.
Data checked 24 October 2026. California data is updated daily.
23
bloom reports since 2016
10 of 11
years with a bloom reported (2016–2026)
1
advisories recommended: 1 Caution, 0 Warning, 0 Danger
Year by year
Each box shows bloom reports logged that year, coloured by the highest advisory recommended.
Reports at Lake Oroville are most often logged in May, June and July.
Recent reports
| Date | Location | Result |
|---|---|---|
| 9 September 2026 | middle fork upstream of Bean Creek | Bloom reported |
| 5 September 2026 | Loafer Creek Campground — Site 65 (coordinates : 39.6152051,-121.4810537) near boat dock a | Bloom reported |
| 29 August 2025 | North Fork | Caution |
| 30 June 2025 | Feathers falls /middle fork | Bloom reported |
| 13 July 2024 | Loafer Creek Recreation Area | Bloom reported |
| 22 May 2023 | Loafer Creek Swim Beach | Bloom reported |
| 16 August 2022 | South fork | Bloom reported |
| 26 April 2022 | near dam | Bloom reported |
| 4 May 2021 | near dam | Bloom reported |
| 29 July 2020 | Lake Oroville, West Branch | Bloom reported |
| 29 June 2020 | Lake Oroville, North Fork | Bloom reported |
| 11 May 2020 | Lake Oroville, near dam | Bloom reported |
What the results mean
Algae may be present. Stay away from scum and discoloured water, and keep pets and livestock from drinking it.
Toxins at higher levels. No swimming, and keep pets and children well away from the water.
High toxin levels. Stay out of the water and off the shoreline.
Dogs and toxic algae
Dogs face the greatest risk because they swallow water and lick algae off their fur. If a bloom has been reported, keep dogs out of the water and away from scum on the shore. If your dog swims in water that might have algae, rinse it with clean water straight away and call a vet if it seems unwell.
Common questions
Is Lake Oroville safe to swim in?
The most recent entry in California's published data is from 9 September 2026: bloom reported (middle fork upstream of Bean Creek). Blooms have been recorded at Lake Oroville in 10 different years, so treat green, scummy or discoloured water with caution. For current conditions, check the California HABs Portal map and posted signs.
When does Lake Oroville get algae blooms?
In the state's records, reports are most often logged in May, June and July. Blooms are most likely in warm, calm weather, but they can appear at other times of year.
Source: California State Water Resources Control Board, official data. This page is independent and not affiliated with the State of California.