Have you ever left a piece of metal in a hot car and it turned into a searing piece of metal? Now imagine being in a suit of metal as it slowly heats up to a searing heat. That's what C3PO had to go through in that suit. I can feel for him. They have a little standing gurney set up for him just so he won't fall down and pass out. "Guys, if I fall, I'm not getting back up."
This is what the characters at your favorite amusement park have to go through every day. It might not be as hot as the desert, but it might as well be inside of one of those giant costumes. Next time you're letting your kid tug on Mickey and chase him around, remember that there's a person inside that costume who is dying a slow and painful death.