48 is probably too cold to paint, but if you keep heat on it it will be fine (again though, don't "burn" it, just keep it warm. If it's white, it's probably primer, so just paint over that. You really need to lightly sand it to scratch the surface so the paint will adhere. If it's a smooth surface, it will likely flake off. Wiping it with dawn/water real good before you paint (after all the prep is done) is also an important step, as if there is wax/oil/contaminants on the surface the paint will not adhere. Just sand very lightly and make a couple passes, just enough to "rough it up", it'll be fine.