When cirrostratus clouds cover the sky, a large ring or halo is sometimes seen around the sun or moon. This is caused by the natural bending of rays of sunlight or moonlight as they pass through the ice particles. Altocumulus clouds are rounded puffs of cloud larger than cirrocumulus. Altostratus clouds cover the sky with a grayish veil through which the sun or moon may shine as a spot of pale light. Nimbostratus clouds are thick, dark, and shapeless and usually bring rain or snow.
Stratocumulus clouds are large and lumpy, round or rolled-looking, and often cover the entire sky.
Stratus clouds are generally dark and appear as streaks across the sky or as a gray layer hanging above the Earth. Stratus clouds are generally shapeless. The various genera, or types, of cloud often merge, making it very difficult to identify a particular cloud formation.