Chicagoland Under Severe Thunderstorm Watch

The prime season for severe thunderstorms in the Chicago area runs from late spring through early fall, when warm, moist air from the Gulf of Mexico clashes with cooler, drier air masses, creating atmospheric instability. These conditions can fuel the development of towering cumulonimbus clouds capable of producing extreme weather. A recent benchmark for severe weather in the region was the derecho on July 15, 2024, which produced a record 32 tornadoes in the NWS Chicago forecast area. That event included four tornadoes within the city limits of Chicago, the most on record for a single day. The most costly thunderstorm event in U.S. history was the Midwest derecho of August 10, 2020, which tracked across Illinois. That storm system caused over $11 billion in damages, with wind gusts estimated as high as 140 mph in some areas, flattening crops and causing widespread, long-lasting power outages for 1.9 million customers. Even less extreme severe storms can have significant impacts. A storm system in May 2025, for instance, led to the City of Chicago dealing with over 200 tree emergencies. That same storm knocked out power for more than 155,000 ComEd customers across Northern Illinois. Historically, the Chicago area has been struck by multiple destructive weather events. The "Plainfield Tornado" on August 28, 1990, was the only F5 tornado ever recorded in the metro area, causing 29 deaths and $165