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No understanding of weather would be complete without learning about clouds. Clouds form when tiny water droplets in the air come together. Stratus are layered clouds. Cumulus are puffy clouds. Cirrus are wispy clouds. Nimbus are rain clouds.
Meteorologists combine these basic names to describe clouds and how high they are in the atmosphere.

l. High clouds are found at the top of the troposphere (the layer of the atmosphere closest to Earth) and are always above 10,000 feet. These include: cirrus clouds (high wispy), cirrostratus clouds (high wispy and layered) and cirrocumulus clouds (high wispy and puffy).

  1. Cirrus clouds are the most common high clouds. Winds blow them into long wisps nicknamed, mares’ tails. They move across the sky from west to east. They are a sign that good weather will follow.
  2. Cirrocumulus clouds are small, rounded puffs of clouds that seem to ripple across the sky in rows, like fish scales. This is nicknamed a mackerel sky.
  3. Cirrostratus clouds are thin sheets of high clouds that spread across the whole sky. They are so thin that they often just look like a hazy sky and show as a ring around the sun or moon. With cirrostratus cloud cover there can still be enough sun to form shadows on the ground.


ll. Middle clouds are found between 6,500 feet and 26,000 feet and include: altostratus clouds (middle layered) and altocumulus (middle puffy).

  1. Altostratus clouds are huge sheets of slate-colored clouds that fill the sky and allow only the dim outline of the sun to be visible and no shadows on the ground. This is sometimes called a watery sun. They often are pushed in front of an incoming snow or rain storms.       
  2. Altocumulus clouds are gray and puffy. They can spread across the sky in little rising masses sometimes called little castles. They are the clouds that, on a hot, sticky summer day, grow into thunderheads later in the day.


lll. Low clouds are found between the ground and 6,500 feet and include: stratus clouds (layered), stratocumulus clouds (low layered and puffy) and nimbostratus (rainy and layered).

  1. Stratus clouds form a low, solid, gray layer across the sky looking like a fog bank that hasn’t reached the ground. They sometimes result in mist and light rain, but more often do not.
  2. Stratocumulus clouds are low bunches of gray clouds that often form at sunset after a storm. They are not a solid band, so blue sky can be seen around them and sunlight will stream down between them often looking like a spotlight from the heavens.
  3. Nimbostratus clouds are dark, wet cloud layers that result in ongoing light to moderate rain. The sun is not visible through them and they don’t allow for shadows on the ground. They make for a very gray day. They often form another a lower ragged layer of clouds that speed by in the wind called scud clouds.


lV. Clouds that Grow and Rise include: cumulus clouds (puffy) and cumulonimbus clouds (rainy and puffy).

  1. Cumulus clouds are probably the most commonly known clouds as they are the cottony puffs that form familiar shapes as they rise. They have flat bottoms that are darker than the rounded tops. And are surrounded by blue sky. They are fair weather clouds. Cumulus clouds can build and rise into giant clouds called towering cumulus.
  2. Cumulonimbus clouds are thunderheads. These are low clouds with dark bottoms that rise into giant rounded tops. When their growing tops hit higher winds, they cut off into an anvil-shape. These could have rain, snow, hail, lightening and even sometimes spawn tornadoes.

Airplanes flying at high altitudes can even form clouds. Contrails are cirrus-like trails of clouds that follow high-flying planes across the sky.

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Amsel, Sheri. "Clouds" Exploring Nature Educational Resource ©2005-2023. February 3, 2023
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