In reply to bobzilla :
Well.... Another way of looking at it is, if you're setting the tire pressures when the vehicle is at a different temperature than the car is being driven at, then the tires are underinflated or overinflated.
When I mount tires in the wintertime, I set them to 4-5psi overinflated in the 60 degree building so that when the vehicle is out in the 10 degree world, they are at the right pressure. Or at least, closer to it.