A Stratus cloud is a cloud belonging to a class distinguished by horizontal layering with a uniform base. This type of cloud is different from other clouds that are usually taller than they are wide (these are known as cumulus clouds). The term “˜stratus’, In Latin, means layer or blanket. Stratus clouds are flat, featureless clouds of low altitude that can vary in color from dark gray to nearly white. A typical cloudy day usually features a sky filled with stratus clouds obscuring the view of the sun. These clouds are more or less above-ground fog formed either from the lifting of morning fog or when cold air moves at low altitudes over a region. Stratus clouds usually do not bring heavy precipitation, although snow and drizzle may occur.
Stratus formations that are accompanied with precipitation are known as nimbostratus. Higher altitude formations are called altostratus and cirrostratus. Cirrostratus clouds are sheet-like and are made up of ice crystals. Though these clouds can be several thousand feet thick and seem to cover the entire sky, they are basically transparent and the sun and moon can sometimes be visible through them. When viewing the moon and the sun through these clouds, they will often appear to have a halo due to light refraction on the ice crystals.