I think this line from the article you linked to is probably the most important/relevant:
Severe Thunderstorms impact a small area, and usually for a brief period of time. I've never once in my life stopped travel for an entire day because of the chance of a storm. There have been times where I've pulled over and/or stopped for a bit to let a storm pass, but that's something you can judge by paying attention to your surroundings.damaging thunderstorms may only affect a fraction of this zone and tornadoes are likely to only affect a tiny fraction
Not to mention, if you're now going through Chicago, then it would seem you'll be traveling north of the area highlighted in the link you provided.