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.

What all this tells us is that hurricanes are much more than just violent, damaging storms. They are giant machines, picking up huge amounts of moisture and energy transporting it from the tropics sometimes as far north as the Arctic circle.

We often ask the question: how will climate change affect hurricanes? Will they get bigger, more frequent, neither, or both? The answer seems to be somewhere in the middle.

But one question that doesn't get asked nearly often enough is: how do hurricanes affect climate?

At the very least, we know that storms move moisture and energy, and that they stir up the ocean, leaving cool water in their wake (see image above). Some research has even suggested that hurricanes could trigger or enhance El Nino conditions in the Pacific Ocean.

Still, whether or not hurricanes have a long-term impact on climate remains an open question, but one that, like the weight experiment, shows that these storms are far more than just random displays of nature's fury.