I think it depends on where you live. If you're in the snow belt where it stays below freezing all winter then you probably don't need to cover. If you're where I live, where we get into the 40's during the day, you better cover. The 6 inches of snow on the top of the pile doesn't blow off or sublime. It's wet and it melts and will soak the top of the wood pile.
Thanks Admin and to all who are responsible for it.