Swimming is prohibited during the ban, which is issued when weather conditions are dangerous or there may be a risk of illness based on monitoring for bacteria in the water, according to the website.
The swim ban was issued because the Metropolitan Water Reclamation District opened the locks at the Wilmette and Chicago River because of the weekend's heavy storms, according to the web site. The swim ban was issued as a precaution.
The park district does have 76 pools throughout the city that will be open for swimming, according to the website.
The Sun-Times Media Wire contributed to this report - Copyright Chicago Sun-Times 2010.)