Alto cumulus clouds are a sign of bad weather to come. When you see them in the autumn season, they are indicating a cold front. When you see them on humid summer mornings, thunderstorms are likely to come durning late afternoon Altocumulus clouds are white/gray and puffy, either floating in a neat row, or scattered across the sky. Theyare usually 1 KM thick. They float 2000-7000 meters in the air. Altocumulus clouds are made mostly out of water droplets, and very little ice crystals.