Grayish or bluish uniform sheet of cloud with very little texture. Usually thicker and grayer and lower in altitude that cirrostratus. Altostratus does not exhibit halos. Dark grey clouds with little visible structure. Usually covers the entire sky and completely hides the sun.
Continuous rain is produced in the summer and snow in the winter.
Low, distinct, grey or whitish cloud elements with a well defined rounded appearance often merged or organized into rolls or streets. The flat even bases have darker patches. Low, uniform, featureless layer of cloud found above a land or water surface. Sometimes produces light drizzle. Known as hill fog when on high ground.