Nimbostratus

How to recognise it

• A uniformly dark grey layer, thick enough that the position of the sun cannot be made out at all.
• A diffuse, ragged base, often blurred by falling precipitation rather than showing a clean edge.
• Small torn fragments of cloud (pannus) drifting below the main layer in the rain.
• No structure, no gaps, no variation in brightness across the sky.

What weather it signals

• Continuous rain or snow, typically lasting several hours rather than minutes.
• The precipitation is steady and moderate rather than heavy and sudden — nimbostratus does not produce thunder, lightning or hail.
• It is the final stage of an approaching warm front, arriving after cirrostratus and altostratus.

How to photograph it

• Protect the lens. This is the one cloud that will actively rain on your equipment.
• Shoot toward a bright patch on the horizon; a fully uniform grey frame is difficult to read as a photograph.
• Include rain-soaked surfaces, reflections or a wet road in the foreground to give the flat light something to work with.

Fun facts

• The Latin nimbus means "rain", making nimbostratus literally the "rain layer" — one of only two genera whose name announces precipitation.
• It is officially classified as a middle-level cloud, even though its base is often low enough to touch hilltops, because the layer itself extends through several altitude bands.
• Nimbostratus is thick enough that it often cannot be photographed from the ground in any way that distinguishes it from a plain grey sky — meteorologists identify it largely by the rain it is producing.

Easily confused with

Frequently asked questions