In the same vein, the house I live in gets extremely hot during the summer, like rainforest hot. I'm out most of the day so the air conditioner stays off and there is no insulation. I wonder, when that time comes, would it be a good idea to keep my stuff in the refrigerator? Obviously warming it before shooting.
go to target or walmart and get a 10 dollar metal lock box. Wrap it and cover it with a couple layers of towels or blankets and then place into a closed cardboard box. This will insulate well and keep the lock box very cool, I have done it before. You could also substitute the cardboard box with a styrofoam cooler.
It would take extreme heat for prolonged periods of time to seriously degrade you gear. I'd imagine sitting in a trunk, which doesn't get too hot, probably not over 100 degrees F, wouldn't cause any or significant problems. As rainjack said, you'd have to worry more about the oil, but this wouldn't affect the concentration of the gear. My opinions anyway. I do not have experience with trunk-stored AAS.
Well, the inside of a vehicle can get a lot hotter than that in some places. Here, a month ago, an infant and a dog died when the mother left them in a locked vehicle. The temperature inside the vehicle was ~130 F. Personally, I could see how temperatures like that for a prolonged period could affect the oil.