Car Wax FAQ. How to protect your paint with a good coat of car wax.
^There's a bit in that article that says that wax will not dry properly in humid or cold weather, so adding moisture directly to the surface of the car won't allow the wax to dry and cure properly. I know this mostly from experience though. This is why the "wax-as-you-dry" products such as QuickWax do not offer a whole lot of protection. They never properly dry.