Aaron Provincial Park - East Beach is sampled monthly from June 1st from September 3th.

Ontario Parks samples beaches weekly from June to the end of August (weather permitting). However, some Parks do not begin sampling until mid June due to factors such as water temperature.

Ontario Parks beaches are monitored according to the province's Beach Management Protocol. The Protocol says that authorities must check water quality at least weekly from June 1 to Labour Day at beaches where there are formal swimming programs or lifeguards. Beaches are typically tested early in the week, on Monday or Tuesday. Samples are processed at provincial labs and therefore processing times vary from park to park, depending on location. Beach postings may occur anytime during the bathing season. As part of the routine monitoring program of public beaches, beach postings may be required where exceedance of recreational water quality levels and other environmental data supports the need for posting. Beaches are posted when the geometric mean of the samples collected exceeds 100 E. coli / 100 ml of water. If the recreational water quality at a swim site meets this standard it is given a GREEN current status in Swim Guide. If the recreational water quality at a swim site exceeds this standard it is given a RED current status in Swim Guide. When water quality exceeds the recreational water quality standards, Ontario Parks posts alerts on their website. Beaches are also physically posted with a sign. Ontario Parks re-samples water that has exceeded the standard as soon as possible.Lake Ontario Waterkeeper enters water quality test results into Swim Guide according to the actual date the sample was taken. Each Ontario Park typically samples its beaches on the same day every week (or month). Ontario Parks has provided us with the sample collection schedule (Mon-Sun) for Ontario Parks' beaches they monitor. We enter water quality data for Ontario Parks according to their sample collection schedule.