Cirrostratus clouds are sheetlike, thin, high-level clouds that occur when cirrus clouds spread out into thin, milky layers. Like all cirrus clouds, they are made of ice crystals. The clouds can cover the whole sky. However, as they are relatively transparent, the Sun or the Moon can easily be seen through them. They usually appear 12-24 hours before rain or snow . They are located above 5.5 km. They are composed of ice crystals which can form halos. These clouds can sometimes be found at the beginning of a warm front which could bring precipitation in the next day. Cirrostratus is a subtype of both cirrus and stratus clouds .
- Above 20,000 feet