Beach Lake Monitoring

UW-Oshkosh collecting a water sampleSeveral locations throughout Lake Winnebago and the Fox River basin are tested weekly for the presence of E. coli bacteria throughout the swimming season from Memorial Day to Labor Day. Beaches may be open, under advisory, or closed based on the level of bacteria. If a water test is concerning, the beach will close for swimming until levels of E. coli bacteria go down. Guidelines are established by the U.S. Environmental Protection Agency.

Beach Status Recommendations:

  • Open: E. Coli bacteria levels are safely below 235 MPN/100 mLs.
  • Advisory: E. Coli bacteria levels are between 235 and 1,000 MPN/100 mLs. Swimming is allowed but caution should be taken. 
  • Closed: E. Coli bacteria levels are above 1,000 MPN/100 MLS. A serious risk of illness may be present. Swimming is not recommended.

Before Swimming:

  • Always look at the water around you before you get in. Conditions can change quickly, and a test result may not always reflect the current water quality.
  • Avoid swimming after heavy rain because bacteria levels in the water may be high.
  • Avoid contact with blue-green algae blooms. They may look blue-green, green, reddish-purple, or brown, and cause the water to be murky.
  • Do not swim or let your pet swim if signs say the water is closed for swimming due to blue-green algae blooms or high bacteria levels.

For more information on beach health safety, please visit the Wisconsin Department of Natural Resources website.

2024 Data Collection begins May 27, 2024

Winnebago County Beach Summary - Week of 8/28/2023

Sample location

date sampled


e. coli mpn

Lake Winneconne Park8/30/202313.5
Fresh Air Park8/30/20231.0
Menominee Park8/30/202316.9


Winnebago County Lake Access Summary - Week of 8/21/2023





Lake Butte des Mortes Boat Landing8/28/20238.6
Lake Poygan Boat Landing8/28/20236.3
Boom Bay8/28/202316.0
Village of Butte des Morts Boat Landing8/28/202313.2
Fritse Park8/28/2023488.4
Asylum Point8/28/202329.2
Black Wolf Boat Launch8/28/20236.3
Grundman Boat LandingThis access point is closed for the yearN/AN/A

Please note: Testing E. Coli at various access points across Lake Winnebago and the Fox River water system gives boaters and other water users a better idea of how water quality can vary across the Fox River Basin within our county.


For an interactive map of these locations, visit

The Winnebago County Public Health Department contracts with the University of Wisconsin-Oshkosh ERIC lab to collect and analyze water samples for E. coli bacteria.