Ask A Met: Can you weigh a cloud? If so, how much would it weigh?

Sara Tonks: Well, it’s complicated. If you have a balloon and you fill it with air, you can weigh the mass of the air, because everything has mass. Clouds are made of water droplets, but you can't exactly weigh a cloud, because the water droplets they are made of are interspersed so far apart in the air. What you could do in a hypothetical world is go up and, like, collect every single water droplet in that cloud, put it in a bucket, and weigh that.

In school at Georgia Tech, one of my professors told me about the spherical cow, which is the idea that it is a lot easier to do math involving cows if we assume they're perfect spheres, which obviously they aren't. We can use that concept with clouds to make the math more reasonable. Assuming a cloud is pretty much a perfect rectangle, 1 kilometer by 1 kilometer, and multiply that by the density of a cumulus cloud, which is on average about 0.5 grams per cubic meter, we can say that the cloud would weigh 1.1 million pounds. That’s the weight of three blue whales!

But that’s just a starting point. Just as there are no spherical cows, there are no perfect clouds in the world. The real world adds in things like hail, and hailstones change the density of a cloud. Storm clouds will be denser than fluffy clouds, because they're heavier with rainwater. You've also got high level clouds, which are less dense because they're icy and thinner up in the atmosphere. Not to mention hurricanes. There’s so much going on with hurricanes!

Do you have a question to ask the meteorologists at Weather.com? Write to us at [email protected] and we’ll pick a new question each week from readers to answer.