One should NEVER apply these products in the sun. The metal on a car gets very hot. because polish and rubbing compound is often solvent based, the product will not cure properly if applied to a hot surface, and a certain amount will evaporate on contact. Further, many polishes and waxes are multi-part compounds which will separate on contact if the surface is too hot. Polish and wax require the same treatment as paint. One needs a cool, dry surface, that is free of dirt, and the appropriate temperature for it to dry or cure properly. Both waxes and polishes must cure to work properly, and this can only be done if they are applied to a dry, cool surface in the shade. Check out the FAQ, 900 which speaks directly to this.