Health advisories were issued Monday for all three of Milwaukee's beaches after heavy rainfall Saturday.

Elevated bacteria levels at South Shore Beach prompted the advisory, which was issued by the city, while pre-emptive advisories were issued due to rainfall at Bradford and McKinley beaches.

Beach advisories are posted if the tested water exceeds 235 colony-forming units, or CFU, of E. coli per 100 milliliters of water. When samples show more than 1,000 CFU per 100 milliliters of water, beaches are closed. E. coli is a common category of bacteria that is regularly used as an indicator of other health risks in the water, like other bacteria, viruses or protozoa.

Friday's water sample at South Shore was 248.1 per 100 milliliters of water, though both samples at Bradford and McKinley were below the threshold of 235 CFU per 100 milliliters of water.

Pre-emptive advisories are posted after heavy rainfall events that may increase the likelihood of unhealthy water quality due to nonpoint pollution from storm water runoff of surrounding surfaces.

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Rain leads to health advisories at three Milwaukee beaches