A Cloud is comprised of either liquids, or solids, or both! Even in the summertime clouds form at such high levels that it's cold enough to snow inside them! Some big thunderstorm (cumulonimbus) clouds have all rain at the bottom, but snow and ice crystals at the top. Now...at all times in our air there is 'water vapor' which is the invisible gas state of water...but if you get enough of it in one area, you're going to condense it into either it's liquid form or freeze it into ice crystals. But once you 'see' a cloud, you know it's either liquid or solid water that is making that cloud.