How heavy is this cloud? That’s what Mary Beth Hall (Member 63,322) found herself wondering as she walked home in Watauga, Texas, US.

You might think of clouds as weightless, but when you add up all the water droplets or ice crystals in clouds, they turn out to be surprisingly heavy. A medium-sized Cumulus, for instance, known as a Cumulus mediocris, which measures about 0.6 miles (1 km) wide, long, and high, contains droplets that add up to around 200,000 kilograms (or 200 metric tons). That’s the equivalent of around 80 adult Asian elephants. The cloud stays up because the water’s divided into tiny particles, each small enough to be wafted up like motes of dust in the air currents within the cloud.

But what about a cloud like the one Mary Beth contemplated? It was a Cumulus congestus, and so much larger than the mediocris size of Cumulus – and one that appears to have been growing into an even larger Cumulonimbus calvus storm cloud. We did some highly technical back-of-an-envelope calculations. Our guesstimate is that the cloud’s volume is around 1,000 times that of a typical 80-elephant Cumulus mediocris cloud. In other words, the droplets (along with any ice crystals) in Mary Beth’s cloud would have weighed something like 80,000 Asian elephants. That’s twice the world’s entire population of Asian elephants. It was a heavy cloud, Mary Beth.