This year has been much more active in terms of severe weather compared to last year. In 2008 Illinois had 47 tornado reports compared to only 23 for 2007. In 2007, Illinois experienced a dry spring with little opportunity for severe weather. This year has seen much more severe weather, both in Illinois and the US.
The NOAA Storm Prediction Center provides detailed reports of severe weather Here are links to the Illinois and US summaries as well as maps generated from their GIS tool:
Chicago-Area Tornadoes in 2008 (click on image for larger map)
Illinois Tornadoes in 2008 (click on image for larger map)
US Tornadoes in 2008 (click on image for larger map)