Cirrus Clouds are one of the three basic cloud forms. The other two
are cumulus and stratus. They are thin, wispy clouds composed of ice crystals and often appear as veil patches or strands. In the mid-latitudes, cloud bases are usually found
between 20,000 to 30,000 feet. Cirrus clouds are the highest clouds that
form in the sky, except for the anvils of cumulonimbus clouds.