Flood Watch

Locations Affected

Chicago, IL ∙ Rockford, IL ∙ Joliet, IL ∙ Aurora, IL ∙ Naperville, IL ∙ Elgin, IL ∙ Waukegan, IL ∙ Cicero, IL ∙ Palatine, IL ∙ Bolingbrook, IL

Full Alert Message

URGENT - IMMEDIATE BROADCAST REQUESTED Flood Watch National Weather Service Chicago IL 221 PM CDT Mon Aug 18 2025 ...FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT... * WHAT...Flash flooding caused by excessive rainfall is possible. * WHERE...For the following counties, in Illinois, Boone, Cook, De Kalb, DuPage, Grundy, Kane, Kankakee, Kendall, La Salle, Lake, Lee, McHenry, Ogle, Will, and Winnebago, and for Lake and Porter counties in Indiana. * WHEN...Through late tonight. * IMPACTS...Creeks and streams may rise out of their banks. Flooding may occur in poor drainage and urban areas. Roads and streets may be flooded. Widespread, significant street flooding possible. Area creeks and streams are already elevated, reducing how much rainfall is needed for flooding to occur. * ADDITIONAL DETAILS... - Soil moisture in many areas is above average to much above average due to recent heavy rainfall. Rivers and streams across northern Illinois are above average to much above average for this time of year. Heavy thunderstorms with rainfall rates of 2 to 4 per hour are possible through tonight, due to atmospheric moisture content much above average for this time of year. If repeated rounds of thunderstorms were to affect the same location, then isolated rainfall totals in excess of 5 inches would be possible. Heavy rainfall is likely to cause flash flooding shortly after onset, especially in urbanized areas and areas that received heavy rainfall over the weekend. - http://www.weather.gov/safety/flood PRECAUTIONARY/PREPAREDNESS ACTIONS... A Flood Watch for flash flooding means rapid-onset flooding is possible, but not yet certain, based upon the latest forecasts. Flash flooding is a dangerous situation. Persons with interests along area rivers, creeks, and other waterways should monitor the latest forecasts and be prepared to take action should flooding develop.

---