My bucket-o-car-wash-solution is always warm but the rinse is always cold since I don't have hot water on the outside. (I have always wanted one of those cool outside showers...at least when I was younger. Could only use it a few months out of the year though!).
Since I always wax the car after I wash it I don't worry about taking off any wax while washing. I figure if I'm taking the time to wash it I might as well take the time to wax it.