Have you ever wondered how much a cloud weighs? Obviously, the answer depends on the size and type of cloud. An average cumulus cloud weighs about 1.1 million pounds or 500,000 kilograms. So, while a cloud may appear fluffy, it’s certainly not light! The surprising weight comes from the enormous number of tiny liquid water droplets suspended within the cloud. Despite weighing as much as dozens of school buses, a cloud remains aloft because each microscopic droplet falls extremely slowly and is continually supported by rising air currents. Here is how scientists estimate the weight of a cloud, why clouds float, and how the weights of different cloud types compare.
Key Takeaways: How Much Does a Cloud Weigh?
- An average cumulus cloud weighs about 500,000 kg (1.1 million lb).
- Cloud weight depends on both its size and the amount of water it contains.
- Clouds are mostly empty space, with tiny water droplets dispersed throughout a huge volume of air.
- A typical cumulus cloud contains roughly 500 tonnes (500,000 kg) of liquid water.
- Tiny cloud droplets fall extremely slowly and remain suspended by rising air currents.
- Thunderstorm clouds can weigh millions of tonnes.
Clouds Are Mostly Empty Space
One reason clouds appear deceptively heavy is that they occupy an enormous volume. Although an average cloud contains hundreds of thousands of kilograms of water, that water spreads through roughly one billion cubic meters of air.
If all of the water in a typical cumulus cloud was collected into one place, it would occupy only about 500 cubic meters. That is enough water to fill a cube about 8 meters (26 feet) on each side or about 132,000 gallons (500,000 liters). The remaining volume of the cloud consists almost entirely of air.
How to Find the Weight of a Cloud
You can’t just place a cloud on a scale and weigh it. Its mass and weight are calculated from its volume and density. Volume is the cloud’s three-dimensional size. Density is the mass of a cloud per unit of volume. To find the mass or weight of a cloud, combine the two values:
Density = mass / volume
solving for mass:
Mass = density x volume
Different types of clouds have different density values. Rain-bearing cumulonimbus clouds are more dense than lacy cirrus clouds. A cumulus cloud is a good starting point for a density calculation because this type of cloud has a fairly regular size and shape. Scientists have measured the average density of a cumulus cloud as about 0.5 grams per cubic meter. Meteorologists use laser Doppler velocimetry to get this value.
One way to measure the size of a cloud is to drive at a fixed rate of speed across its shadow when the sun is directly over head. If you know the speed and how long it took to cross the shadow, you can find the length of the shadow, which is the same as the length of the cloud at noon:
Distance = speed x time
Using this method, a typical cumulus cloud is about 1 kilometer or 1000 meters across. While clouds aren’t perfect cubes, the width and height of a cumulus cloud are about the same as its length, so the volume is:
Volume = length x width x height
Volume = 1000 meters x 1000 meters x 1000 meters
Volume = 1,000,000,000 cubic meters
Clouds are gigantic! Next, plug in the density and volume values to find a cloud’s mass, which is also its weight on Earth.
Mass = density x volume
Mass = (0.5 grams/cubic meter) x (1,000,000,000 cubic meters)
Mass = 500,000,000 grams or 500,000 kilograms
Converting this value to pounds, the weight of a cloud is 1.1 million pounds.
Cirrus clouds are smaller and less dense, so they weigh less than cumulus clouds. Cumulonimbus clouds are much larger and denser than cumulus clouds, so they weigh much more. A cumulonimbus cloud can weigh 1 million tonnes.
Typical Weights of Different Cloud Types
| Cloud Type | Typical Weight | Characteristics |
|---|---|---|
| Cirrus | Tens to hundreds of tonnes | Thin, high clouds made mostly of ice crystals |
| Cumulus | About 500 tonnes | Puffy fair-weather clouds |
| Stratocumulus | Hundreds to thousands of tonnes | Low, layered clouds |
| Nimbostratus | Thousands to millions of tonnes | Thick rain-producing clouds |
| Cumulonimbus | Millions of tonnes | Towering thunderstorm clouds |
What Weighs as Much as a Cloud
It’s hard to visualize what 1 million pounds looks like. To put it into perspective, the weight of a cloud is about the same as:
- 3 blue whales (375,000 pounds each)
- 100 elephants
- 40 school buses
- about $20,000,000 in US quarters
- Airbus A380 passenger jet (1.1 million pounds)
- Union Pacific Big Boy steam locomotive (1.2 million pounds)
- Antonov An-225 Mriya cargo aircraft (1.28 million pounds)
- Power station transformer (1.28 million pounds)
Why Clouds Don’t Fall
If clouds are so massive, why don’t they fall from the sky? The answer is that they would, if there wasn’t anything between them and the ground. But, clouds rest on a layer of air that is dense enough to support them. You can think of clouds as ships that sail on a sea of air. The reason the air is more dense than the cloud is because the air and cloud aren’t the same temperature. Also, clouds are dynamic. Evaporation and condensation of water occur within the cloud. These changes of state of matter absorb and release energy, changing the temperature within a cloud. Sometimes the air around a cloud becomes warm enough that it can absorb a cloud. The cloud becomes water vapor dispersed in the air and shrinks or disappears. Other times, clouds do become too heavy to remain aloft. Each cloud droplet is extremely small, usually only 10 to 20 micrometers (µm) in diameter. Because the droplets are so tiny, air resistance nearly balances the force of gravity, giving them a terminal velocity of only a few centimeters per second. They may sink toward the ground or release precipitation in the form of rain or snow.
How Scientists Measure the Water in a Cloud
Meteorologists cannot place a cloud on a scale. Instead, they estimate its liquid water content (LWC), which is the amount of liquid water suspended within a given volume of cloud.
Scientists measure liquid water content using research aircraft equipped with cloud probes, laser Doppler instruments, weather radar, satellites, and computer weather models. Fair-weather cumulus clouds typically contain about 0.2 to 0.8 grams of liquid water per cubic meter, with 0.5 g/m³ commonly used as an average value for calculations. Dense storm clouds often contain several times more water.
How Much Water Is Inside a Cloud?
Since nearly all of a cloud’s mass comes from its suspended water droplets, the weight of a cloud is essentially the weight of the water it contains.
For an average cumulus cloud:
| Property | Typical Value |
|---|---|
| Water mass | 500,000 kg |
| Water volume | 500 m³ |
| Water in liters | 500,000 L |
| Water in U.S. gallons | About 132,000 gal |
Although this sounds like an enormous amount of water, it is divided among billions of microscopic droplets spread throughout the cloud.
Mass vs. Weight
Strictly speaking, mass and weight are not the same thing.
Mass is the amount of matter an object contains and its units are kilograms. Weight is the force of gravity acting on that mass and its units are newtons.
In everyday conversation, people often use the terms interchangeably. On Earth, a cloud with a mass of 500,000 kilograms has a weight of approximately 4.9 million newtons.
Why Clouds Look White
Clouds appear white because the tiny water droplets inside them scatter all wavelengths of visible sunlight nearly equally. Since all colors scatter together, the cloud appears white to our eyes.
Thicker clouds often appear gray because less sunlight reaches their lower portions. During storms, the cloud becomes so thick that it blocks much of the incoming sunlight, making the underside appear dark.
Common Misconceptions
Myth: Clouds consist of water vapor.
Fact: Clouds consist primarily of tiny liquid water droplets or ice crystals. Water vapor itself is invisible.
Myth: Clouds float because they are lighter than air.
Fact: Individual water droplets are denser than air, but they are so small that air resistance and rising air currents keep them suspended.
Myth: A cloud has a solid or fluffy surface.
Fact: Flying through a cloud feels much like flying through fog because clouds are simply collections of tiny suspended droplets.
Myth: Heavy clouds should immediately fall to the ground.
Fact: The water spreads through an enormous volume, and each microscopic droplet falls so slowly that upward-moving air can easily keep it suspended.
FAQs
Can you stand on a cloud?
No. A cloud is simply a region of air containing microscopic water droplets or ice crystals. It has no solid surface to support weight.
How much does a thunderstorm cloud weigh?
A large cumulonimbus cloud can weigh millions of tonnes, depending on its size and the amount of water it contains.
Are clouds made of water vapor?
No. Clouds are made primarily of tiny liquid water droplets or ice crystals. Water vapor is invisible.
Do clouds become heavier before it rains?
Yes. As water droplets collide and merge, they become larger and heavier. Once they become too heavy for upward air currents to support, they fall as precipitation.
Is fog a cloud?
Yes. Fog is simply a cloud that forms at or very near the ground.
References
- Freud, E.; Rosenfeld, D. (2012). “Linear relation between convective cloud drop number concentration and depth for rain initiation”. Journal of Geophysical Research. 117 (D2). doi:10.1029/2011JD016457
- Grenci; Lee M.; Nese, Jon M. (2001). A World of Weather: Fundamentals of Meteorology: A Text / Laboratory Manual (3rd ed.). Kendall/Hunt Publishing Company. ISBN 978-0-7872-7716-1.
- Jaramillo, A.; Mesa, O. (June 19, 2017). “On the relative density of clouds.” Quarterly Journal of the Royal Meterological Society. Vol. 144; Iss. 707, pp. 2650-2653. doi:10.1002/qj.3099