No wax will repel heat. But a well prepped surface will be glossy and reflect more light which will allow the for a marginally cooler surface and wax will help protect and slightly enhance the gloss.
If you want to wax a black car in a hot climate, best to stick with a synthetic wax/sealant as natural waxes break down in the heat rather quickly. Duragloss 105 Total Performance Polish, Meguiars Ultimate, and Finish Kare Hi Temp Wax FK1000 are my go to synthetic waxes.
Last edited by Robenstein; 05/30/16 12:33 PM.