We got the rain to move out fairly early, but it stayed cloudy as you mentioned. Just off the top of my head, a few events that had preceding rain or clouds and then produced a good amount of severe wx in the LOT cwa are 4/20/04, 6/5/10 and 6/30/14... granted they mainly impacted areas near/south of I-80.
I don't think we were all that far away from having a more significant severe wx episode in the area on Wed. I mean, even with all the clouds, ORD managed to reach the low 70s and dews got into the low 60s.