Heat - what does it do to a digital camera?

Besides what JD said, if you use the camera when hot expect to see lots of noise. For most CCDs every 6°C increase in temperature doubles the noise level.

I have seen a small film camera warped/melted from the sun when left in the car. None of the buttons/controls would move.

Be sure to vent (slightly opened windows) the car if you leave it inside the car for too long. Cover it loosely with a light colored cloth out of the suns rays.I would not leave it in the glove box either.