I feel like next week is the last best shot for the elusive 100 reading at ORD (would already pencil in Midway with north of 50% odds, lol). August does not look particularly cool to me, but the window for that kind of thing is starting to close.
We are already going to be fighting climo as only 23% of Chicago's 100+ days have come in August/September, and the last one to occur in one of those months was back in 1991.