New York
Toxic algae in Jefferson County lakes
15 lakes and waterways in Jefferson County have harmful algal bloom reports in New York's official data. The most recent entry is for Butterfield Lake: Butterfield Lake was on New York's harmful algal bloom list on 11 September 2025, with confirmed bloom status (1 report). Butterfield Lake, Payne Lake and Lake Ontario and 3 more have had blooms in three or more years.
Lakes with bloom history
Newest report first. Each lake has its own page with the full history and what the results mean.
Other waterbodies with a report
These have one or two reports in a single year, which isn't enough history for a page of their own yet.
- Greenwood Lake 2023
- Kents Creek 2025
- Lake Of The Woods 2015
- Muskellunge Lake 2020
- Sixberry Lake 2015
- Sixtown Pond/Crystal Lake 2016
Source: New York State Department of Environmental Conservation (DEC), official data, checked 24 October 2026. For today's conditions see the NYHABS map. No report doesn't mean a lake is safe: most water is only tested occasionally.