Krull Park Beach in Olcott was reopened Saturday after the Niagara County Department of Health rescinded its beach advisory.
The beach was closed to swimming Thursday after high levels of E. coli bacteria were found in Lake Ontario water samples taken the previous morning.
Ronald Gwozdek, principal public health engineer for the Niagara County Health Department, said thunderstorms Tuesday and Wednesday churned up the lake's water, causing the rise in bacteria readings at the surface. It was the second time the beach was closed to swimming this season.
New tests conducted Friday showed the water was suitable for swimming. The Health Department planned to continue to monitor water quality.