A cloud is a large group of tiny water droplets that we can see in the air.
Clouds are formed when water on Earth evaporates into the sky and condenses high up in the cooler air. Learn more about the water cycle.
Rain, snow, sleet and hail falling from clouds is called precipitation.
Most clouds form in the troposphere (the lowest part of Earth’s atmosphere) but occasionally they are observed as high as the stratosphere or mesosphere.
Clouds can contain millions of tons of water.
There are a range of different types of clouds, the main types include stratus, cumulus and cirrus.
Stratus clouds are flat and featureless, appearing as layered sheets.
Cumulus clouds are puffy, like cotton floating in the sky.
Cirrus clouds are thin and wispy, appearing high in the sky.
There are many variations of these 3 main cloud types including stratocumulus, altostratus, altocumulus, cirrostratus and cirrocumulus.
Fog is stratus type of cloud that appears very close to the ground.
Clouds can also be made of other chemicals.
Other planets in our Solar System have clouds. Venus has thick clouds of sulfur-dioxide
while Jupiter and Saturn have clouds of ammonia.
Check out this cloud basics video for more