Cloud PointField Guide

Mid cloud — genus

Nimbostratus

The thick, sunless rain- and snow-maker

Written by Laurence WayneEntry No. 41Common

Nimbostratus: The thick, sunless rain- and snow-maker
Plate XLIPhotograph by Gabriel Picard, CC BY-SA 4.0.

Nimbostratus is a grey, often dark cloud layer whose appearance is rendered diffuse by more or less continuously falling rain or snow that usually reaches the ground. It is thick enough throughout to completely blot out the sun, showing no shadows and no internal detail. It forms as a deep moist layer is lifted slowly and steadily — typically the broad ascent ahead of a warm front — thickening until it precipitates for hours. Ragged low scud often forms beneath it.

Worth knowing

  • Nimbostratus can extend vertically for over 3km, making them one of the thickest cloud types.
  • The precipitation from these clouds can last 12-24 hours continuously.
  • They're so thick that even at midday, it can feel like twilight beneath them.
  • Ancient meteorologists called these clouds 'the rain bringers' - and they were right!
Note

Still unsure it's the same cloud? Our app, Cloud Point— on iOS and Android — reads a photo and returns the likely type with altitude, useful when a formation is fading faster than you can look it up.

In motion

Test yourselfThree levels

Choose a difficulty

What weather does nimbostratus typically bring?

  1. aBrief sunny spells
  2. bSteady, prolonged rain or snow
  3. cDry, gusty winds only
  4. dLightning with no rain
Show answer

AnswerSteady, prolonged rain or snow

Nimbostratus produces more or less continuous precipitation that usually reaches the ground.

Why can't you see the sun through nimbostratus?

  1. aIt is always night-time
  2. bThe layer is thick enough throughout to blot out the sun
  3. cIt is made of black soot
  4. dThe sun is blocked by the moon
Show answer

AnswerThe layer is thick enough throughout to blot out the sun

By definition nimbostratus is thick enough throughout its depth to completely obscure the sun.

Altostratus and nimbostratus can look alike. What marks the change to nimbostratus?

  1. aIt lifts to become a high cloud
  2. bIt thickens and deepens until steady precipitation reaches the ground and it completely blots out the sun
  3. cIt breaks apart into separate puffy lumps
  4. dIt takes on a distinct blue colour
Show answer

AnswerIt thickens and deepens until steady precipitation reaches the ground and it completely blots out the sun

Altostratus thickening into nimbostratus is marked by continuous rain or snow reaching the ground and a layer dense enough to hide the sun entirely.

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