Thunderstorm Wind in Williamson County, Illinois

Widespread wind damage occurred countywide. Extensive tree and power line damage resulted in power outages up to several days long. Many power poles were snapped. Countywide, efforts to restore power were complicated by swampy fields, mud, and downed trees. Ninety-five percent of the county was without power at the peak of the outages. Numerous permanent structures were damaged, including major businesses in downtown Marion and Herrin. A total of 33 homes were heavily damaged or destroyed. It is estimated that over 10,000 homes in the county received minor damage (less than 50,000 dollars per house). Gas leaks were common. Most communication by phone was impossible, including cell phones. Stores were closed, making groceries and gas very difficult to obtain locally in the immediate aftermath of the storm. Travel was nearly impossible due to debris and trees blocking roads. While about two dozen people were treated for storm-related injuries at local hospitals, all but one of them was due to post-storm cleanup. Many school facilities were damaged. The roof of Carterville High School was severely damaged. Several windows were blown out of the school. Minor damage occurred at athletic facilities, including the roof blown off a baseball dugout. Many outbuildings and small structures were destroyed across the county. In Carterville, a garage was lifted and dropped on a vehicle. Many vehicles countywide were damaged or destroyed by falling tree and building debris. A state disaster declaration was granted. A dusk-to-dawn curfew was imposed, and a state of emergency was declared. The Williamson County airport near Marion reported a peak gust of 86 mph. Based on the most severe structural damage east of the airport, peak winds were estimated by storm surveyors close to 100 mph. There was extensive damage at the airport, including hangar buildings. A television station on Route 13 was knocked off the air due to structural and roof damage. All along Route 13, signs were blown down, power poles were down, and windows were smashed. Car dealerships along Route 13 sustained damage due to signs falling on vehicles and windows being blown out. Numerous structures sustained varying degrees of roof damage. A large hotel near the Interstate 57 interchange sustained major roof damage. Many trees were down along Interstate 57 from the Route 13 interchange northward, blocking the southbound lanes. Semis on the interstate were overturned or blown off the highway, causing extended traffic delays. One of the drivers of the semis was seriously injured. A tree fell on a van on the interstate. Damaged or destroyed trees were too numerous to count. Cleanup was expected to last through Labor Day, according to the Mayor of Marion.

A mature, very intense derecho moved rapidly east along a stationary front across the Mid Mississippi Valley into the Lower Ohio Valley. With a very moist and unstable atmosphere, along with strongly veering winds aloft, embedded tornadic supercells were associated with the derecho. Widespread damaging winds were the primary impact. Nearly all the damage in southern Illinois was associated with the comma head at the northern end of the bow echo. Winds were measured slightly over 100 mph under the comma head as it passed through the Carbondale area. In addition to damaging winds, the slow-moving storm complex dumped very heavy rain that flooded roads.