The thin, layered Cirrostratus cloud is composed of ice crystals and forms a veil that covers all or part of the sky.
Height of base: 18,000 - 40,000 ft
Latin: cirrus - lock or tuft of hair; stratus - flattened or spread out
Cirrostratus are transparent high clouds covering large areas of the sky. They sometimes produce white or coloured rings, spots or arcs of light around the sun or moon that are known as halo phenomena. Sometimes they are so thin that the halo is the only indication that a cirrostratus cloud is in the sky.
Cirrostratus can span thousands of miles, and may be smooth or fibrous and are often fringed with cirrus clouds.
Shadows will normally still be cast by the sun when shining through cirrostratus clouds, which can help distinguish them from similar nimbostratus clouds.
Last updated: 6 August 2014