The rainy season is during the summer (Northern Hemisphere's winter). Outside of those months it doesn't rain very often! I've spent two winters (June-August) in Namibia and can't recall much, if any rain. But now that we're approaching summer there, I imagine there's a little more rain. The Namib desert (which is a small percentage of Namibia, to be clear) is one of, if not the, driest deserts in the world.