Heavy Chicago Rains Cancel River Swim Fundraiser As McCook Reservoir Nears Capacity

Chicago weather flooding concerns dominated the weekend as persistent rain and stormy conditions swept through the region, ultimately forcing organizers to cancel one of the city’s newest and most distinctive charity fundraisers while pushing local infrastructure to its limits.

Heavy Rainfall Triggers Flooding Concerns

By 1 p.m. Sunday, many areas across Chicago had recorded between 2 and 3 inches of rainfall over the previous 48 hours, according to the National Weather Service. Forecasters issued a hazardous weather outlook Sunday morning highlighting continued thunderstorm activity, an elevated flooding risk throughout the region, and a swim risk specifically affecting Lake Michigan beaches.

NWS meteorologist Zachary Yack explained that multiple waves of rain and thunderstorms had moved through the area, with some locations experiencing particularly torrential downpours. He noted that rainfall of this magnitude creates genuine threats of localized flooding along with rising river levels throughout the affected areas.

Water Infrastructure Under Strain

The Metropolitan Water Reclamation District of Greater Chicago issued an Overflow Action Day alert, urging residents to limit their water usage given that most Chicago area sewer systems carry combined sewage and stormwater together, a setup that can lead to overflow situations during periods of heavier rainfall.

The region’s extensive Tunnel and Reservoir Plan, infrastructure specifically built to capture excess combined sewer water during storm events, reported rising water levels throughout its various reservoir sites. The southwest suburban McCook reservoir reached 95 percent capacity by Sunday, a level significant enough that the system began releasing some combined storm and sewer water into local waterways starting around 5 a.m. Sunday, according to MWRD Executive Director John Murray.

By contrast, the district’s south suburban Thornton reservoir, which had experienced record-breaking water levels during storms earlier this summer, remained at a much more manageable 17 percent capacity as of Sunday, highlighting the uneven distribution of rainfall impact across different parts of the region.

Weekend Events Disrupted By Weather

The persistent stormy conditions significantly affected two major events scheduled for Sunday in Chicago, resulting in one complete cancellation and a delay for the other.

Organizers of the Chicago River Swim announced early Sunday through social media that they were canceling the event entirely, citing both weather conditions and the state of the river itself as primary factors. This particular race, which debuted just last year, challenges swimmers to navigate the Chicago River’s main downtown branch, an event designed to showcase successful river cleanup efforts while simultaneously raising funds for ALS research, the fatal neurological condition also known as Lou Gehrig’s disease.

Separately, the ongoing storms had already forced an early closure of Riot Fest Saturday night, with organizers subsequently delaying the festival’s Sunday reopening until 2 p.m., timing that aligned with when forecasters expected the bulk of the rainfall to finally clear the area.

Looking Ahead To Drier Conditions

Yack indicated that by Sunday afternoon, most of the heavy rainfall had moved through the region, with only occasional light rain expected to continue before tapering off sometime Sunday night. He offered an optimistic outlook heading into the new week, suggesting the forecast looks mostly dry for the days ahead.

According to the National Weather Service forecast, Chicago faces just a 20 percent chance of showers before 1 p.m. Monday, on what’s otherwise expected to be a cloudy and breezy day. Conditions should improve further by Tuesday, with clouds breaking to allow some sunshine through. Both days are expected to see high temperatures settling in the mid-60s, offering residents some relief after a particularly soggy and stormy weekend.