Let's break it down, using forecasts from the NWS Storm Prediction Center.
Five percent (brown) is the significant threshold. Note that a broad band from Ottawa to Chicago to Detroit has double that risk. Note: 10% means there is a ten percent change of a tornado within 25 mi. of any give point in the risk area.
Damaging Wind Threat
Here, 15% (yellow) is the significant threshold. In addition to the 30% area, the hatching means
Large Hail Threat
There is a significant risk (yellow or red) of large (≥1") all the way from Kansas City to Syracuse.
O'Hare has average 3 hour delays that will only get worse. Delays are also reported from Midway. The best idea would be to see if your airline will re-route you around the storms (e.g., if you are traveling from Salt Lake City to Richmond via Chicago on United, see if they will route you through Houston).
Here is the radar at 11:55am. It is a mess! Airline conditions in the region will only get worse today.
Given the recent wet conditions, high winds will be able to topple trees more readily than in average conditions. This may resort in power failures given the forecast of very high winds. If you have a generator, make sure it has adequate fuel. If you don't, make sure your flashlights, cell phone and computer are fully charged before the storms approach. Of course, you'll want to unplug sensitive electrical items as the storms approach due to the possibility of power surge damage.