At least six tornadoes confirmed after derecho sweeps through Iowa, Illinois and Indiana

A mesoscale convective system (MCS) that moved from eastern Iowa to northern Indiana on August 11 was preliminarily confirmed as a derecho.

The system began around 07:00 CDT in Iowa (12:00 UTC) on August 11 and continued through at least 13:25 EDT (17:25 UTC) in Indiana, according to the Storm Prediction Center.

The agency said it would assess whether the later continuation toward Cincinnati should be included in the derecho track.

“The storm complex has been preliminarily confirmed as a derecho, with most of the damage due to straight-line winds, with some significant damage,” the NWS Quad Cities office said. Their survey teams confirmed three EF1 tornadoes in Delaware County, Iowa, during the morning phase of the derecho.

A 4-year-old boy was killed when a tree fell onto the bedroom of a home in Geneva Township, Indiana, during storms, according to the Jennings County Sheriff’s Office.

NWS Chicago survey teams confirmed three additional tornadoes with damage consistent with EF1 intensity. Damage along a path from near Monee through Crete was consistent with up to EF1 intensity. A second tornado produced damage indicating at least EF1 intensity from southern Orland Park toward Flossmoor.

Damage associated with a third tornado in the Minooka area was consistent with EF1 intensity.

Two of the Chicago-area tornadoes continued across the state line into Lake County, Indiana. One affected St. John, while the other affected Munster.

The maximum measured gust associated with the derecho was 160 km/h (99 mph) at Gary, Indiana. Other measured gusts included 121 km/h (75 mph) at Plymouth, 119 km/h (74 mph) northwest of Michigan City and 114 km/h (71 mph) at Knox-Starke County Airport.

More than 600 000 utility customers in Illinois and Indiana lost power during the storms, with Lake and Porter counties in Indiana and Will County in Illinois among the hardest-hit areas.

Flights were temporarily halted at Chicago O’Hare International Airport and Chicago Midway International Airport as the storms crossed the region.

The system produced widespread tree, power-line and structural damage across northern Illinois and northwestern Indiana. Roads were blocked by fallen trees, and extensive outages continued into the evening.

It is worth noting that SPC had not yet determined whether the system’s continuation into southeastern Indiana and toward Cincinnati would be included in the derecho track.

SPC said the official determination for the event would be made in 2027 after 2026 Storm Data is finalized.

Severe storms leave at least two dead, spawn at least six tornadoes, and cause flooding across the Midwest and Ohio Valley

References:

¹ Severe Weather (Including a Derecho) on August 11th, 2026 – NWS – August 11, 2026

² Recap of the August 11, 2026 Morning Derecho – NWS – August 11, 2026