Grundy County, IL

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From the Forecaster

Threat for Flash Flooding Tonight

Created by the NWS Chicago WFO

Showers and thunderstorms with torrential downpours are expected to develop again across northern Illinois this evening and continue into Sunday morning. This rain will fall over already saturated ground from the past day, increasing the risk for localized flooding in poor drainage, low-lying areas, and urban areas.

Headline: Threat for Flash Flooding Tonight. Sub Headline: Main time window for flash flooding late this evening through into Sunday morning. What To Expect. Another round of torrential rainfall. May flood roads, low-lying areas, fields, and basements, and cause rapid stream/creek rises. When: Favored Timing of Highest Rainfall Rates. ~7 PM this evening - 6 AM CDT Sunday. Where: Areawide. Highest rainfall amounts and greatest flooding impacts favored across northern Illinois and far northwest Indiana, which aligns with much of the area that experienced heavy rain over the past day. What To Do. NEVER drive or walk across flooded roads! Move valuables from flood-prone areas, such as basements and outdoor areas with poor drainage. Graphic Created: Saturday, September 19, 2026 2:27 PM CDT
Chicago Area Forecast Discussion

Seven-day Weather Risk Overview

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