Weekly testing by the Windsor-Essex County Health Unit has uncovered elevated bacterial levels at most local beaches.
The latest results, released on Friday, showed E. coli levels exceeding 200 at five of the area's seven active beaches.
This places the beaches under a "code yellow", meaning that swimming is not recommended. The beaches themselves and other amenities, though, are operating normally.
The beaches include Cedar Beach and Cedar Island Beach in Kingsville, Holiday Beach in Amherstburg, Lakeview Park West Beach in Lakeshore, and Seacliff Beach in Leamington.
Higher levels of bacteria may pose an increased risk to swimmers of intestinal illness, infection, or skin problems.
Colchester Beach in Essex and Point Pelee North West Beach in Leamington tested within normal E.coli levels and are fully open.
Sandpoint Beach in Windsor is closed indefinitely due to safety concerns.
