Cirrostratus may cover the sky as a continuous sheet with no features, but it often has a fibrous look. The cloud is so thin it is almost transparent. You can see the sun or moon through it much more clearly than you can through altostratus, and this is the simplest way to tell one cloud from the other. Also, if the sun or moon is surrounded by a halo, the cloud is almost certainly cirrostratus. It is worth watching cirrostratus, because it often signals changing weather. If it forms from cirrus that grows thicker and more continuous, it may give way to altostratus followed by lower cloud and wet weather. If gaps begin to appear in cirrostratus, so that it slowly changes into cirrocumulus, the weather is probably fair and may remain dry for several days.

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