The Windsor-Essex County Health Unit is not recommending swimming at four local beaches this weekend.
High levels of bacteria were detected at Mettawas Beach and Cedar Island Beach in Kingsville, West Belle River Beach in Lakeshore and the Hillman Marsh Beach in Leamington.
The health unit conducts beach water quality monitoring at ten public beaches every Wednesday from June to September.
Officials warn that water quality can change from day to day and they do not recommend swimming if there was recent heavy rainfall, if the water is cloudy or if you are unable to see your feet in the water.