My wife and I are scheduling a trip to the North Chicago area for the last week or so of September. Having never been in that part of the country, we're curious to what we may expect in weather conditions. We don't know exactly when colder air starts moving in and could scoot that date forward by a month if needed. We'll be making the trip in a cage (boo) but wondering what the weather might be like for sight seeing and such. My son and his family moved there in Jan., so he has no experience of the change of seasons. Any help would be appreciated.