Documentation of damages caused by severe weather is crucial in many insurance claims. Typically, these inquiries involve home owners trying to document hail damage to cars or houses. Unfortunately, reports of storm damage are usually limited to the more spectacular events. Furthermore, the time between the event and the release of official reports can be several months. The reports are collected by the local National Weather Service (NWS) offices from their own logs, media accounts, and reports from local officials. Once collected, they are forwarded for archival at the National Climatic Data Center in their monthly report called Storm Data.
Here are some useful links that can aid in the search for storm reports. Some of these sites contain unofficial preliminary reports that may be changed or added to in the later official documents.
Current Severe Weather Reports - NOAA Storm Prediction Center
Search the national database - NOAA National Climatic Data Center searchable database on storm data
Official Storm Data publication - NOAA National Climatic Data Center monthly reports
Storm data for Northeast Illinois - NWS Chicago office