How Much Does a Cloud Weigh?

iStock / B&M Noskowski
iStock / B&M Noskowski

Reader Jane wrote in to note that clouds look so nice and fluffy and lighter-than-air, so they certainly can’t weigh much. Right? 

When Peggy LeMone was in junior high, a friend’s dad pondered that same question, and she kept it in the back of her mind for years. Now all grown up, LeMone is a researcher at the National Center for Atmospheric Research, and she’s figured out an answer. Today, she shares her cloud-weighing technique with us. 

First, figure out how dense the cloud is. Scientists have measured the water density of a typical cumulus cloud (the white, fluffy ones you see on a nice day) as 1/2 gram per cubic meter—about a small marble’s worth of water in a space you and a friend could comfortably sit in. The density will be greater for different types of clouds. 

Next, figure out how big the cloud is. By measuring a cloud’s shadow when the sun is directly above it, you can get an idea of its width. LeMone does this by watching her odometer as she drives under a cloud. A typical cumulus, she says, is about a kilometer across, and usually roughly cubical—so a kilometer long and a kilometer tall, too. This gives you a cloud that’s one billion cubic meters in volume. 

Do the math with the density and volume to determine the total water content of the cloud. In this case, it's 500,000,000 grams of water, or 1.1 million pounds. That’s a lot of weight to wrap your head around, so LeMone suggests putting it in more familiar terms, like elephants. That cloud weighs about as much as 100 elephants. If you’re a Democrat and you’re feeling partisan, she says, you could substitute 2500 donkeys. If you care more for dinosaurs than politics, you could also say the cloud weighs about as much as 33 apatosauruses.

If all those elephants or donkeys or dinosaurs were hanging out in the sky, they’d fall. So how does a several-hundred-ton cloud stay afloat? For one thing, the weight isn’t concentrated in a hundred elephant-sized particles or even a billion marble-sized ones. It’s distributed among trillions of really tiny water droplets spread out over a really big space. Some of these droplets are so small that you would need a million of them to make one raindrop, and gravity’s effect on them is pretty negligible. 

What’s more, the cloud is less dense than dry air, so it's buoyant. It also helps that all those little droplets get some lift from updrafts of warm air. Those droplets don’t float forever, though. When the cloud’s water density increases and the droplets get bigger and heavier, the cloud eventually does fall, bit by little bit, in the form of rain. 

Celebrate the Holidays With the 2020 Harry Potter Funko Pop Advent Calendar

Funko
Funko

Though the main book series and movie franchise are long over, the Wizarding World of Harry Potter remains in the spotlight as one of the most popular properties in pop-culture. The folks at Funko definitely know this, and every year the company releases a new Advent calendar based on the popular series so fans can count down to the holidays with their favorite characters.

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Right now, you can pre-order the 2020 edition of Funko's popular Harry Potter Advent calendar, and if you do it through Amazon, you'll even get it on sale for 33 percent off, bringing the price down from $60 to just $40.

Funko Pop!/Amazon

Over the course of the holiday season, the Advent calendar allows you to count down the days until Christmas, starting on December 1, by opening one of the tiny, numbered doors on the appropriate day. Each door is filled with a surprise Pocket Pop! figurine—but outside of the trio of Harry, Hermione, and Ron, the company isn't revealing who you'll be getting just yet.

Calendars will start shipping on October 15, but if you want a head start, go to Amazon to pre-order yours at a discount.

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100 Fascinating Facts About Earth

The best Spaceball.
The best Spaceball.
NASA

Did you know that there’s a place in the South Pacific Ocean called Point Nemo that’s farther from land than any other point on Earth? So far, in fact, that the closest humans are usually astronauts aboard the International Space Station. (And by the way: The map you’re about to look for Point Nemo on might not be entirely accurate; a certain amount of distortion occurs when trying to depict a 3D planet on a 2D surface.)

In this all-new episode of The List Show, Mental Floss editor-in-chief Erin McCarthy is journeying to the center of the Earth, and visiting its oceans, its atmosphere, and even space, in search of 100 facts about our endlessly fascinating planet.

The subjects that fall under the umbrella of “facts about Earth” are nearly as expansive as Earth itself. Geology, biology, astronomy, and cartography, are all fair game—and those are just a few of the many -ologies, -onomies, and -ographies you’ll learn about below. 

Press play to find out more Earth-shattering facts, and subscribe to the Mental Floss YouTube channel for more fact-filled videos here.