The annual Chicago River Swim was canceled early Sunday as heavy rainfall continues to pummel the Chicago area.The race organizers said the potential for sewer overflow impacting water quality and the risk for lightning contributed to their decision to cancel. It would have been the second Chicago R iver race in nearly 100 years.The National Weather Service issued a flood advisory early Sunday as forecasters expect the rain to continue into Monday. Heavy rainfall and thunderstorms started Saturday across the Chicago region.Over 550 flights were delayed and 49 were canceled at O'Hare International Airport from Saturday morning to Sunday morning, according to the Chicago Department of Aviation. At Midway International Airport, one flight was canceled and 56 were delayed in that same time period. Day two of Riot Fest was cut short Saturday because of "torrential downpours." Rain chances will persist through Monday, though threat of heavy rainfall should end by early this afternoon. Dry, but cooler than average weather can be expected by mid-week. #ILwx #INwx pic.twitter.com/v86GOTOB33— NWS Chicago (@NWSChicago) September 20, 2026 ...read more read less