A nimbostratus cloud is a multilevel, amorphous, nearly uniform, and often dark-grey cloud that usually produces continuous rain, snow, or sleet, but no lightning or thunder.
Although it is usually a low-based stratiform cloud, it actually forms most commonly in the middle level of the troposphere and then spreads vertically into the low and high levels. Nimbostratus usually produces precipitation over a wide area.
The prefix nimbo- comes from the Latin word nimbus, which denotes "dark cloud".
Downward-growing nimbostratus can have the same vertical extent as most large upward-growing cumulus, but its horizontal expanse tends to be even greater.
