I am a little paranoid with my games and try never to leave them in a car longer than it takes me to get to a destination. I was always very aware of our hot humid weather and how it affects cardboard. apparently, the heat affects those plastics more and faster, something I hadn't even thought about.
Glad I saw this post as I was going to take my copy in the car with me when we go away this weekend, having second thoughts now.
For what it's worth: I had my copy in a parked car in Southern CA heat for ~9 hours a couple days ago and nothing happened. However after seeing this I'm not going to do that again. Not worth the risk.