The Nimbostratus Principal Cloud Type contain primarily suspended water droplets and continuously falling raindrops and/or snow. The water droplets may be super-cooled meaning the liquid is below the freezing point. The precipitation usually reaches the ground as continuous rain or snow. Nimbostratus is diffuse and lacks a discernable cloud base because of precipitation aloft or reaching the ground. It is common for very low fractostratus clouds to be visible under the nimbostratus due to high relative humidity and rain. Lightning, thunder, or hail are not present.

Nimbostratus usually begin as Altostratus (but on rare occasions start as Altocumulus or Stratocumulus and thicken through a depth of thousands of feet due to the moistening of the layer by precipitation. This results in a continuous cloud that eventually occupies both the middle and lower levels.

Examples of Nimbostratus

Rain was falling when the images below were taken.

Format: genera (Example: Nimbostratus); Nimbostratus is the genera. There are no species or variety sub-types.