GlossaryCirrostratus
Genus · High · Cs
Cirrostratus
Cirrostratus
Definition
A genus of high cloud forming a transparent, whitish veil of ice crystals, usually covering much or all of the sky. The sun's disc remains visible through it, though it may be fuzzy, and a 22° halo is common.
Field note
Cirrostratus is the cloud that gives halos. Its thickening marks the second stage of a warm front; rain follows in roughly 6 to 24 hours depending on the speed of approach.
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- 3 July 2026
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Read the full field note
Cirrostratus: the veil that gives you a halo
Cirrostratus is the cloud that makes the sky look like frosted glass. It is a thin, continuous, whitish veil of ice crystals at 5500 metres and above, and it is responsible for almost all the halos you will ever see. It is also the second step in the frontal sequence that ends in rain.