Flash Flood — Cook, Illinois

2025-08-18 to 2025-08-19 · near Lansing, Cook, Illinois

Event narrative

An estimated 700 structures were flooded in southeast Cook County, including Dolton, Harvey, South Holland, and Thornton. Two lanes of I-294 near the quarry in Thornton were covered in water. Damages in the area are estimated at around $3.5 million.

Wider weather episode

During the afternoon and evening of the 18th, a few rounds of thunderstorms brought torrential rainfall to much of northern Illinois resulting in flash flooding. One particularly strong storm also produced damaging winds in DeKalb County. Initial reports estimate $8.8 million in flood damages around northern and northeast Illinois, and around $2.5 million in the city of Chicago alone.

View location on OpenStreetMap → (41.5647, -87.5587)

Source: NOAA Storm Events Database, event_id 1292415. Narrative written by the NWS forecast office that issued the report.