Nimbostratus clouds are the thick, gray rain clouds that spread out across the whole sky and block the Sun completely.
Nimbostratus clouds are low to mid-level, dense, and layered clouds that produce continuous, steady precipitation in the form of rain or snow.
They typically form between 600 and 3,000 metres, though their tops can extend higher into the mid-troposphere.
Unlike convective clouds, nimbostratus clouds are associated with widespread, persistent precipitation rather than isolated showers or thunderstorms.
They usually develop from thickening stratus or altostratus layers as warm or occluded fronts advance.
- Height: Low to middle levels, ~2,000–10,000 ft
- Look: Thick, dark, and featureless layers
- Name meaning: Nimbus = rain, Stratus = spread out
- Rain: Steady rain or snow
What do Nimbostratus clouds look like?
Nimbostratus are broad, dark gray sheets that stretch across the sky without much shape. They’re often so thick that the Sun disappears completely behind them.
Nimbostratus clouds are uniform, dark grey, and featureless, lacking the distinct vertical development of cumulonimbus clouds. They often cover the sky extensively, creating overcast conditions and reducing sunlight penetration.
How do they form?
They usually develop as altostratus clouds thicken and lower during the approach of a warm front. Unlike fluffy cumulonimbus (storm clouds), nimbostratus are more about long, steady precipitation.
What weather do they bring?
These are the “all-day rain” clouds. Nimbostratus bring continuous, widespread rain or snow that can last for hours. They don’t have the lightning or thunder of storm clouds, just persistent wet weather.
A history of Nimbostratus clouds
The standard name is nimbostratus (Ns). The prefix nimbo- indicates rain-bearing, while stratus indicates a layered form.
The name was solidified in modern meteorological classification; Luke Howard did not explicitly define nimbostratus in his original scheme, but his “nimbus” concept for rain clouds was part of his system.
The International Cloud Atlas (from 1896) and later editions formalised nimbostratus.
