Especially in a car with no A/C.
Mid 90's today, and unfortunately there weren't any underground spots left in the parking garage. I think I lost about 5 pounds in sweat on the drive home. :)
Here's how hot it gets in a car after 3 hours in direct sunlight:
That's the worst example, but every disk in the box is unusable, and the box itself is a little warped. :(