The Windsor Essex County Health Unit has posted a warning for swimmers at just one public beach in the region this week, Lakeshore Lakeview Park West Beach.
The e.coli count was 969 there this week.
Swimming is not recommended when the e.coli count is that high.
The health unit gave the all clear for swimming at the region's six other public beaches, Cedar Beach, Cedar Island Beach, Colchester Beach, Holiday Beach, Point Pelee Northwest Beach, and Seacliff Beach.