The distinctive anvil shape of the enormous Cumulonimbus storm cloud (see examples below) is only visible when you look at it from many miles away – 20 or 30 miles is not a bad distance. If you are anywhere near it, the whole sky is covered with its dark, ragged underside. You can then distinguish it from the other dark rain cloud, Nimbostratus, by the fact that its moisture falls in sudden, heavy showers, rather than steady, prolonged precipitation. A Cumulonimbus also produces thunder, lightning and often hail.