Clouds can make or break our day.
They are what deliver the precipitation all life on Earth depends on. They also make us more comfortable. On a hot day, a large cloud blocking the sun is as welcome as a drink of water. In the winter, a layer of clouds can insulate us, preventing temperatures from dropping.
Clouds add beauty to the world, too. Have you ever seen a breathtaking sunrise or sunset without a cloud in the sky? Probably not, because the clouds are what add color to these picture-perfect moments.
Sometimes, clouds simply bring us joy. Who hasn’t spent time simply watching the clouds roll by? Or looking for fun shapes hidden within these giant puffballs?
But what is a cloud really? Essentially, clouds are masses of ice crystals or water droplets that are suspended in the sky. Clouds form when air in the sky becomes cooler, causing the water vapor to condense into liquid form.
All clouds contain water vapor, but not all clouds produce rain. Rain occurs when water droplets join together to form larger droplets. When the droplets become large enough, gravity causes them to fall to the ground in the form of rain, snow, sleet or freezing rain.
Clouds can have many different shapes and appearances. Some are dark and threatening, others are thin and wispy. Still others are big and fluffy. There are 10 main types of clouds, and they are classified by their elevation, shape and structure. Based on elevation, clouds are classified as high, mid-level or low. High clouds are 16,500 feet to 45,000 feet above the ground, while mid-level clouds are 6,500 feet to 23,000 feet above ground and low clouds are less than 6,500 feet above ground.
When it comes to the many different kinds of clouds, you may notice that some of the same root words are included in many clouds’ names. That’s because in the early 1800s, an amateur meteorologist named Luke Howard proposed a naming convention for clouds that is the foundation of the classifications that are still used today. Howard recognized four cloud types and named them using Latin words:
Cumulus: Heaped or in a pile
Stratus: In a layer or sheet
Cirrus: Hairy, curled or thread-like
Nimbus: Bearing rain
Here is a closer look at the many different types of clouds that add dimension to the sky.
High clouds
The highest clouds are typically thin, wispy clouds that look like streaks in the sky. They are not usually thick or dense enough to block out the sun. There are three kinds of these high clouds: cirrus, cirrocumulus and cirrostratus clouds.
The thinnest and patchiest of the high clouds are the cirrus clouds, which usually look like small patches or narrow bands. Cirrus clouds often are red or yellow in color just before sunrise or just after sunset. Because of how light filters through, they light up before other clouds do and the color will fade from them later. Even during the day, cirrus clouds near the horizon may have a golden yellow color.
Cirrocumulus clouds are also thin enough for the sun to shine through, but they often look like long rows or thin, rounded puffs. They are usually a bright white, but they can sometimes look gray. These clouds are most common in winter and are a sign of cold, fair weather.
Words to know
Precipitation: A product of the condensation of water vapor that falls to the ground in the form of rain, sleet, snow or ice.
Elevation: The height of something above a given level, usually sea level.
Cirrostratus clouds are thin sheets of clouds that usually blanket the entire sky, but they aren’t thick enough to block the sun or even the moon from shining through. These clouds often signal a change in weather, because they usually appear about 12 hours to 24 hours before rain or a snowstorm.
Mid-level clouds
Mid-level clouds mainly consist of water droplets or, when it is cold enough, ice particles. Altocumulus clouds are puffy, and they typically appear in clumps or layers. They are usually darker in some parts than others. These are the most common of the mid-level clouds.
Altostratus clouds form sheets or layers that blanket the entire sky. Sometimes the layers will be thin enough that the sun appears faintly behind them, but they can also sometimes reach higher up into the sky, as high as the high-level clouds.
Like altostratus clouds, nimbostratus clouds can also extend high in the sky. These clouds can form layers thick enough to block the sun, and they often have ragged-looking clouds at their base. Nimbostratus clouds produce precipitation, usually longer-lasting rain or snow showers and not storms or short bursts of rain or snow.
Low clouds
Low clouds are those that are closest to the ground, no more than 6,500 feet above Earth’s surface. These include what are probably the most recognizable clouds: cumulus clouds. These are the puffy, cotton ball clouds that dot the sky on a nice day. Cumulus clouds come in all shapes and sizes, which make them the perfect kind of cloud for finding shapes in the sky. Cumulus clouds are a bright white color where they are lit by the sun, but underneath they may appear darker.
Cumulonimbus clouds are low-lying clouds, but they often rise high up into the atmosphere, as high as some of the high-level clouds. These are our thunderstorm clouds, and they are associated with heavy rains and even hail and tornadoes.
Stratocumulus clouds look lumpy or patchy and they are usually gray, although they may look bright white at the edges where the sun hits them. Sometimes light precipitation, like patchy drizzle or snow flurries, falls from stratocumulus clouds. These clouds are similar to altocumulus clouds, but they often appear puffier and more patchy in the sky.
The last type of low-lying cloud is the stratus cloud. These clouds form thick layers that blanket the sky. On a mostly cloudy day, it’s often stratus clouds that block out the sun. Stratus clouds can produce light drizzle or snow if their cloud layer grows thick enough.
Special clouds
A few types of clouds don’t fit into the standard categories and exist as special types of clouds. These include contrails, which are created by jets flying high above Earth. Many people don’t consider these to be clouds, but they are because they are made from condensed water droplets.
Another type of cloud we see from time to time are mammatus clouds. These clouds are actually a specialized form of other types of clouds, such as cumulonimbus and cirrus clouds, that appear to have pouches hanging down from them. The pouches form when cold air contained in the clouds begins to fall toward Earth. These types of clouds often accompany thunderstorms, but they themselves do not cause severe weather.
Two other kinds of special clouds, lenticular clouds and orographic clouds, are typically formed in part by the ground under them. Lenticular clouds are thin and flat, like flying saucers. They often get their shape because of the hilly terrain underneath them, or because of how air rises up on flat ground. Orographic clouds are most common over hilly or mountainous terrain that forces air to flow over or around them. They’re also seen in places where two air masses meet.
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