WGN-TV Tom Skilling Weather Center, Bill Snyder, Tom Valle
1 hour ago
From the National Weather Service:
The heaviest rainfall was observed near Aurora, Illinois, with a maximum spot rainfall of 16.94 inches in a 24-hour period. The 24-hour rainfall measured near Aurora remains a statewide record (as of 2022). The far west end of Chicago saw 10.99 inches of rainfall, which remains the highest storm total ever observed in Chicago (as of 2022). These extreme rainfall amounts caused widespread and severe flooding in Chicago’s western suburbs and areas immediately west of it. Flooding was observed in the Fox River, DuPage River, and Des Plaines River, as well as tributaries such as Blackberry Creek, Sawmill Creek, and Lemmon Tran. Many river maximum records remain to this day (as of 2022). Damage was estimated at $600 million to $700 million ($1.1 billion to $1.3 billion in 2022 values). FEMA estimated that more than 35,000 homes were flooded.
Relatively large areas received unusually large amounts of rainfall. An area of about 100 square miles near the heaviest rainfall areas averaged an estimated 16.3 inches, and an area of about 1,000 square miles averaged about 12.6 inches.
Rainfall data was collected from hundreds of gauges and the extent of the event was mapped. A rainfall contour map published in a technical report produced a few months after the event is shown below (Angel et al. 1997). In 2020, new radar bias correction techniques were used to combine rain gauge and radar data to produce estimated rainfall maps. The latest analysis suggests that rainfall more intense than the maximum recorded may have occurred southwest of Aurora. A wide area experienced rainfall that has less than a 1% chance of occurring in a given year.
Information on this page was compiled from several sources, including contributions by former Illinois State Climatologist Jim Angell. Further details about this flood are provided in the technical report “Record-breaking Storm in Northern Illinois, July 17-18, 1996” (Angel et al. 1997). Inflation-adjusted damage figures are derived from the U.S. Bureau of Labor Statistics’ CPI Inflation Calculator.
