It seems impossible. Clouds float gently across the sky, drifting and shape-shifting. How can something that looks so airy weigh anything at all? But scientists have measured: an average cumulus cloud - the medium fluffy white kind - contains roughly a million pounds of water. That’s about the weight of 100 elephants.
Each cloud is made of trillions of tiny water droplets (or ice crystals). Each droplet weighs almost nothing, but multiply that by trillions and you get serious mass. So why do they float? It’s not that they’re light - it’s that the air below them is warm and rising, providing a constant updraft that supports the droplets in mid-air.
Storm clouds are even more dramatic. A really big thunderstorm cloud (cumulonimbus) can hold over a billion pounds of water. When all that water can no longer be supported as droplets - usually because they’ve grown big enough to fall faster than the air can push them up - it falls as rain. That’s why heavy thunderstorms can dump so much water so fast: there’s already an enormous amount waiting up there.
