Grey Bruce Health Unit is advising bathers not to swim at Little River Park Beach in Thornbury.
According to a media release from the health unit, beach water sampling identified bacteria levels "in excess of Ministry of Health and Long-Term Care standards."
The health unit indicated the results are "consistent with high wave action and significant rainfall over the last few days."
Those visiting the beach are reminded the high bacteria levels may pose a risk to health, particularly if any water is ingested.
The health unit will be testing the water again next week to determine the safety of the beach.
In general, bathers are advised to avoid swimming after heavy rain or in cloudy water.