Cirrus

Height of base: 18,000 - 40,000 ft

Latin: cirrus - lock or tuft of hair

Cirrus are short, detached, hair-like clouds found at high altitudes. These delicate clouds are wispy with a silky sheen or look like tufts of hair. In the day time, they are whiter than any other cloud in the sky. While the sun is setting or rising, they may take on the colours of the sunset.

Cirrocumulus

Height of base: 20,000 - 40,000 ft

Latin: cirrus - lock or tuft of hair; cumulus - heap

Cirrocumulus clouds are lots of small white clouds - called cloudlets - grouped together at high levels. Composed almost entirely from ice crystals, the little cloudlets are regularly spaced, often arranged as ripples in the sky. They are relatively rare, and unlike altocumulus clouds, never have any shading.

Cirrostratus

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.