Cloud Facts



  • Clouds are dense masses of water drops and ice crystals that are so tiny they float high in the air.
  • Cumulus clouds are fluffy white clouds. They pile up as warm air rises and cool to the point where water vapour condenses.
  • Strong updraughts create huge cumulonimbus, or thunder, clouds.
  • Stratus clouds are vast shapeless clouds that form when a layer of air cools to the point where moisture condenses. They may bring long periods of light rain.
  • Cumulonimbus thunder clouds are the tallest clouds, often over 10 km high.
  • Cumulus clouds build up in fluffy piles as warm, moist air rises. Once it reaches about 2000 m, the air cools enough for clouds to form.
  • Cirrus clouds are wispy and form so high up they are made entirely of ice. Strong winds blow them into ‘mares tails’.
  • Low clouds lie below 2000 m above the ground. They include stratus and stratocumulus clouds (the spread tops of cumulus clouds).
  • Middle clouds often have the prefix ‘alto’ and lie from 2000 m to 6000 m up. They include rolls of altocumulus cloud, and thin sheets called altostratus.
  • High-level clouds are ice clouds up to 11,000 m up. They include cirrus, cirrostratus and cirrocumulus.
  • Contrails are trails of ice crystals left by jet aircraft.