It's hard to think that anything floating in the sky could be heavy. But a great piece on NPR (video) shows just how weighty clouds, thunderstorms, and even hurricanes can be.
According to Andrew Heymsfield of the National Center for Atmospheric Research, even a single, small puffy cloud can have 400 tons of water in it, or the equivalent weight of 100 elephants.
The numbers get staggering as the clouds get bigger. Sticking with the elephant unit, Heymsfield estimated that a typical thunderstorm cloud - a cumulonimbus - has 15 million elephants worth of water floating in the air at any given time. The warm, moist updrafts that feed them can pour 500 elephants into the storm each second.
Predictably, hurricanes are even more immense. You ready for this? Heymsfield calculated that the 2005 storm Hurricane Rita held 100 million elephants' worth of water as it spun through the Gulf of Mexico at its height.
How does all this water stay afloat? Simply put, updrafts. Clouds and storms are driven by warm, moist air that rises up off Earth's surface, then cools and condenses. As long as there is a steady supply of rising air, cloud droplets are buoyed up and can't fall. If the droplets get big and heavy enough, they will eventually come down as rain.