EF1 tornado in La Salle County, Illinois

A tornado with peak winds of 100 mph touched down south of Marquette Street west of La Salle Street. The tornado impacted several businesses ripping off well anchored roofing material and snapping a utility pole at its base. The roof of a flooring business was blown off and hit a nearby building. It was here the tornado reached peak intensity. The tornado continued east ripping shingles off of roofs of buildings and houses and shredding trees. One tree was shredded badly near Canal Street and a large tree limb fell onto a new pickup truck causing significant damage. Fallen trees and tree limbs covered most areas along the path to the Fox River. The tornado is believed to have lifted in an inaccessible forested area east of the Fox River. Eye witnesses indicated the tornado may have had multiple vortices with clear rising and rotating motion of debris.

During the late morning through the afternoon of Monday August 10th, a line of intense thunderstorms known as a derecho brought widespread severe wind damage across Iowa, northern Illinois and northern Indiana.

In north central and northeast Illinois alone, the severe winds of 60 to 100 mph downed or damaged tens of thousands of trees, as well as caused severe damage to homes, businesses, and infrastructure. There were 10 injuries reported in north central and northeast Illinois within the NWS Chicago/Romeoville County Warning Area (CWA). Local officials estimated that nearly one million customers lost power across northern Illinois at the height of the derecho and some people were without power for several days. Damage was estimated to be in the hundreds of millions of dollars in north central and northeast Illinois, with several billions of dollars in damages across the entire Corn Belt region including significant damage to crops and agriculture infrastructure. While much of the damage was due to straight line winds, there were also 14 tornadoes documented in north central and northeast Illinois.

The combination of high moisture, explosive instability and very strong atmospheric wind flow for mid-summer had developed quickly over the Corn Belt region on the morning of August 10th. This resulted in a progressive, well-organized complex of storms for hundreds of miles and at times traveling nearly 70 mph. After bringing extensive damage from extreme wind speeds in Iowa that morning, the damage transitioned across northern Illinois from widespread wind damage to narrow, brief and intense swaths associated with compact circulations within the thunderstorm line, some of which were associated with tornadoes.