I live in Mesa, Arizona, and I am also concerned about the foam type airplanes that I have! It will get up to 100 + degrees in my garage during the summer, so I have the same concerns that you do. Everything I have heard is as long as the plains are not exposed to the direct sunlight and not in any type of moisture situation, most likely will not have any problems. I do store all my batteries in an ammo can and in a conditioned space. Other than that everyone I have talked with say we will be OK!

Hope this will ease your mind a little!

Rob
TWD