Clouds and fog Clouds are usually the most obvious feature of the sky. They both reflect weather patterns and play a role in what the weather does. In addition to their obvious role as sources of precipitation, clouds also can affect the temperatures of the places below them. Clouds not only block incoming sunlight during the day, which cools the air, but they can also block outgoing radiation from the Earth, which can warm temperatures. Many unanswered questions about Earth's climate revolve around the roles of clouds.
Clouds also create some patterns of light in the sky such as halos.
Below those links are several links to information about clouds. High-level clouds are composed of ice crystals and tend to be very thin and wispy. The names of clouds usually indicate both the cloud's location in the sky, as noted above, and its type, as listed below. The listings below give several examples of cloud names. Fog is a cloud on the ground.