I've never seen the autostop feature not work because the temperature was too hot, only when it was too cold. I do live in Chicago, it's true, but I got the car back in August and there were some hot days at the end of the summer, so I think I would have noticed if that was happening. Still, you've made me want to check the manual to see if there's an upper temp limit as well as a low one, and find out what it might be.