Record-breaking tornado outbreak struck Chicagoland on July 15

CHICAGO - On the evening of July 15, a powerful complex of thunderstorms swept through Chicagoland, producing widespread damaging winds and a record-breaking 31 tornadoes.

This outbreak marks the most prolific tornado event in the history of the Chicago National Weather Service (NWS) forecast area. The previous record for a single event was 22 tornadoes, set during the June 30, 2014, and March 31, 2023, outbreaks.

The National Weather Service officially classified the storm system as a derecho, a widespread, long-lived windstorm associated with a band of rapidly moving thunderstorms. For a storm to be deemed a derecho, the wind damage must extend more than 240 miles, with wind gusts of at least 58 mph along most of its path.

Northern Illinois and Indiana are no strangers to derechos, averaging one per year. However, derechos as strong as the one on July 15 occur only once every 5 to 10 years.

The severe weather did not begin on July 15; the Chicago area also experienced tornadic activity the night before, on July 14. The NWS confirmed that seven tornadoes touched down that Sunday. Combining the two consecutive severe weather events, a total of 38 confirmed tornadoes occurred within a 36-hour period across the NWS Chicago forecast area.

This historic outbreak highlights the importance of preparedness and awareness during severe weather season in the Midwest.