Science & Nature
Half a Foot of Rain in 4 Days Strained Chicago Region’s Stormwater System
(Steve Godomski / iStock)
The Chicago region is drying out after a soggy stretch that saw multiple rounds of storms dump upwards of half a foot of rain on some municipalities.
The city of Chicago’s official weather gauge at O’Hare Airport measured 2.78 inches of precipitation between Thursday and Sunday, but that total scarcely tells the story of the wider metropolitan area.
Gauges near Midway Airport recorded 5 inches of rain over the same period, while Bridgeview, Oak Lawn and Palos Park all measured 5.41 inches, according to a report from the Chicago office of the National Weather Service.
Naperville tallied 6 inches, and 6.75 inches fell in Sugar Grove in Kane County.
The wet weather wreaked havoc on weekend event schedules, including Riot Fest in Douglass Park, which shut down early on Saturday and opened late on Sunday.
The much anticipated Chicago River Swim, scheduled for Sunday morning, was canceled altogether due to weather-related concerns including the risk of lightning and the potential for combined sewer overflows that could affect water quality.
Video: A combined sewer overflow at the MWRD’s North Branch Pumping Station on the Chicago River, Sept. 20, 2026. (Patty Wetli / WTTW News)
Those concerns proved well-founded, as the heavy influx of stormwater taxed the region’s sewer system.
Combined sewer overflows were recorded at multiple locations on the Chicago River, meaning untreated storm and waste water was released into the waterway rather than being conveyed to a treatment plant. Overflow locations included the North Branch Pumping Station near Lawrence and Francisco avenues, and the Racine Pumping Station adjacent to Bubbly Creek.
The Deep Tunnel’s McCook reservoir and tunnels were at 97% capacity on Monday, holding 5 billion gallons of combined storm and waste water. McCook serves central Chicago and three dozen suburban municipalities.
Contact Patty Wetli: [email protected]
