The Niagara Region is once again offering beach water testing results.
Officials test water quality at 19 beaches across the region, and post the results online.
Currently, four beaches are posted as unsafe for swimming.
Beaches are posted as unsafe for swimming when water tests show unacceptable levels of E. Coli bacteria.
"The levels of E.coli are affected by a number of conditions including birds, wildlife and large numbers of swimmers.
Swimming in these waters could cause infections of the ear, eye, nose, throat and skin as well as cause diarrhea if the water is ingested."
Officials say the beach might also be unsafe or closed because of other environmental conditions including excessive algae growth, flooding, garbage or debris, spills, and bad odours.
Weather conditions can also affect test results, including heavy rainfalls, and high winds.
Along with checking water quality before heading to the beach, residents should also check rules since many beaches have implemented new policies to cut down on crowds.