Free Pictures & Descriptions of Storm Clouds, Stratus, and Cumulus

What are the different types of clouds? I became fascinated with clouds while homeschooling my son. While learning about the environment and science we did a project studying clouds. Feel Free to copy any of these cloud pictures for yourself or your student. For more detailed information scroll down the page.

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What is a Cloud?

Clouds are made up of water drops or ice crystals that settle on dust particles floating in the sky. There are many kinds of clouds. Some are big and puffy on warm days, and other clouds bring precipitation, such as rain and snow.

Why does a cloud form?

The sky can be full of water but most of the time the drops of water are too small to see. The drops have turned into a gas called water vapor. As the vapor raises higher in the sky the air gets cooler. The cooler temperatures make the water droplets start to stick to things like bits of dust, sea salt or ice.

This clumping of condensing water vapor is a Cloud. When the air from the Earth’s surface is lifted towards the atmosphere, both the air pressure and temperature drop. As soon as the air temperature reaches the air’s dew point, (what is dew point?) the water vapor condenses and forms clouds.

Dew Point – condensed water is called dew when it forms on a solid surface. The dew point is associated with humidity. A relative humidity of 100% indicates the dew point is equal to the current temperature and that the air is maximally saturated with water.     

Why are the clouds dark before a storm?

If a cloud is filled with a large amount of water molecules or is super thick sunlight cannot pass through causing the cloud to appear very dark.

What causes Rain?

Most of the water in clouds is in very small droplets. They are so light they float. When the water droplets join with other droplets they become larger and gravity makes them fall to the Earth. This is called rain. If the air is cooler it may form snowflakes.

What are the different types of Clouds?

Clouds get their names in 2 ways. The types are classified by height and appearance.

  • One is where they are found in the atmosphere. High in the sky or low clouds form closer to Earth’s surface. When low clouds touch the ground it is called fog. Middle clouds are found between low and high clouds.
  • The other is, clouds are named by their shape. Cirrus are high and look like feathers. Cumulus are middle and look like cotton balls. Stratus are low and look like bed sheets.

How many types of clouds are there?

The three main types of clouds are called cirrus, stratus, and cumulus.

There are many other subtypes, 10 or more…kinds of cloud names, such as altocumulus and nimbostratus that get their names from combining two kinds of clouds or some other factor.


Cumulus clouds are probably the most recognized clouds and typically form when warm air rises and reaches a level of cool air, where the moisture in the air condenses. These clouds form below 6,000 feet but in some extreme cases they can be in altitudes as high as 39,000 feet. They look like white, puffy cotton balls. The reason cumulus appear fluffy is because bubbles of air, called thermals, linger in the cloud. Cumulus clouds are formed by warm air rising which then cools and condenses.

In windy conditions, the clouds can form lines called cloud streets that are parallel with the wind. In mountainous areas, they may also form lines at an angle to the wind, due to the presence of lee waves above the clouds. The most common Lee Wave is mountain waves. Wave clouds do not move downwind as clouds usually do, but remain fixed in position relative to the obstruction that forms them.

 Lenticular clouds form on the downwind side of mountains.Wind blows most types of clouds across the sky, but lenticular clouds seem to stay in one place. Air moves up and over a mountain, and at the point where the air goes past the mountaintop the lenticular cloud forms, and then the air evaporates on the side farther away from the mountains.

 Cumulus humilis clouds, appear as small  or medium-sized puffy shapes, often occurring in times of fair weather. However, cumulus clouds can grow into cumulonimbus clouds which are larger and often spread out in a shape of an anvil or plume.  Cumulonimbus may produce heavy rain, lightning, severe and strong winds, hail, and even tornadoes. Cumulus congestus clouds, which appear as towers, will often grow into storm clouds, cumulonimbus.

Stratocumulus clouds are part of the LOW cloud group. These clouds are low, lumpy, and gray. Stratocumulus clouds can look like cells under a microscope – sometimes they line up in rows and other times they spread out. Only a drizzle or light precipitation occurs with these cloud types.

Stratocumulus clouds form in altitudes below 6,000 feet.  A low layer of stratocumulus clouds appear near sunset and are the spreading remains of larger cumulus clouds.  Altocumulus clouds differ from Stratocumulus  because they are slightly smaller. One easy way to determine if the cloud is altocumulus or stratocumulus is to hold your hand up to the sky,  altocumulus clouds are about the size of a human thumb nail while stratocumulus clouds are the size of a fist.

Altocumulus clouds are part of the Middle Cloud group (2,000-7,000m, 6,000-20,000 ft). They are grayish-white with one part of the cloud darker than the other and look like parallel bands of cotton balls. Altocumulus clouds are formed from a slow uplift of warm air from a cold front pushing its way near the ground. If you see these clouds on a warm humid morning, by late afternoon it is a very good chance you will have thunderstorms.

 Nimbostratus clouds belong to the Low Cloud  (surface to 2000m, below 6,000 ft) group. They are dark gray with a ragged base. Nimbostratus clouds are associated with continuous rain or snow. Sometimes they cover the whole sky and you can’t see the edges of the cloud.

Stratus clouds belong to the Low Cloud (surface-2000m, below 6,000 ft) group. These clouds form when weak upward air currents lift thin layers of air high enough to start condensation of excess water vapor when the air temperature falls below the dew point. They are uniformed layered, gray in color and can cover most or all of the sky. Stratus clouds can look like a fog  and are associated with overcast weather. Only drizzle comes from Stratus clouds, if heavier rain falls then their title is changed to nimbostratus.

  Altostratus clouds are in the MIDDLE Cloud group ( 6,000 to 20,000 feet). They are very thin and uniform, gray or blue-gray, covering most of the sky to create overcast. Altostratus are translucent enough to see the sun or moon through them and are associated with coming rain. These clouds are incapable of producing heavy precipitation, but may have light drizzle. Nimbostratus clouds follow altostratus clouds. Nimbostratus are in the LOW Cloud group (below 6,000 feet). They are dark clouds that bring moderately heavy prolonged precipitation. When the temperatures get below freezing, Nimbostratus clouds can contain ice crystals. Broken up clouds called fractostratus clouds can lie below the Nimbostratus.

Cumulonimbus clouds are a result of atmospheric instability. These clouds can form alone, in clusters, or along a cold front. They can create hail and lightning and other dangerous severe weather.

Cumulonimbus clouds belong to the thunderstorm clouds or clouds with vertical growth group. Reaching heights to 10km, high winds will flatten the top of a cumulonimbus cloud out into an anvil-like shape. Cumulonimbus clouds, also called Storm Clouds, cause heavy rain, lightning, hail, snow and tornadoes. See the pictures of Cumulonimbus, Storm Clouds.

Cumulus clouds, which indicate low-level atmospheric moisture often precede storms. In this picture of a Cumulonimbus cloud or thunderstorm cloud, much lightning was occurring with the winds increasing rapidly. The rarest thunderstorm type, the supercell, produces the most violent weather including the most significant tornadoes, giant hail, deadly lightning and damaging microburst winds.

This picture of a storm cloud was during the start of a monsoon. We watched it forming and moving incredibly fast over our area.

Mammatus clouds are pouches of clouds that hang underneath the base of a cloud. They are usually seen with cumulonimbus clouds that produce very strong storms. Mammatus clouds look like a field of tennis balls, melons, or like female breasts. That is where the name comes from.  

Cirrus clouds are the most common in the HIGH cloud (5000-13000m) group. They are white and predict fair weather even though they are so cold and composed entirely of ice. Cirrus clouds are the highest in elevation consisting of long, thin, wispy streamers. and consist of long, thin, feathery streamers. Cirrus clouds often mark the start of a warm front and approaching bad weather. They are the fastest moving cloud because the wind current is very strong at that altitude.

Cirrustratus clouds form in the 18,000 feet and above. The refraction of light by the ice crystals in the Cirrostratus clouds cause a halo around the sun or moon. You can not see the halo when this happens but the sun or moon will be less visible because the clouds condense too much for clear visibility. clouds are usually white and predict fair weather. These clouds often follow Cirrus Clouds therefore Cirrostratus clouds are indicators of good weather.

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