@Grivusangel -- In my experience, making caramel frosting, or anything candy-like, should be done when it's cold, clear and the humidity is low. But the powdered sugar recipe may be one to look for.
I love caramel apples, myself. I've done the melt the wrapped caramels thing, and the make it from scratch, but I'll admit: the caramel "wraps" you peel off the wax paper and wrap around the apple are the easiest to deal with, and they're not sensitive to temperature or humidity. So what if they're not the kind you get at the fair? I don't have a copper candy making pot like the pros do and it's not easy to get caramel to do what it's supposed to do without breaking it or burning it. The wraps are a cop-out and that's fine with me.