Rain Facts



  • Rain falls from clouds filled with large water drops and ice crystals. The thick clouds block out the sunlight.
  • The technical name for rain is precipitation, which also includes snow, sleet and hail.
  • Drizzle is 0.2-0.5 mm drops falling from nimbostratus clouds. Rain from nimbostratus is 1-2 mm drops. Drops from thunderclouds can be 5 mm. Snow is ice crystals. Sleet is a mix of rain or snow, or partly melted snow.
  • Rain starts when water drops or ice crystals inside clouds grow too large for the air to support them.
  • Cloud drops grow when moist air is swept upwards and cools, causing lots of drops to condense. This happens when pockets of warm, rising air form thunderclouds – at weather fronts or when air is forced up over hills.
  • In the tropics raindrops grow in clouds by colliding with each other. In cool places, they also grow on ice crystals.
  • The rainiest place is Mt Waialeale in Hawaii, where it rains 350 days a year.
  • The wettest place is Tutunendo in Colombia, which gets 11,770 mm of rain every year. (London gets about 70 mm.)
  • La Reunion in the Indian Ocean received 1870 mm of rain in one day in 1952.
  • Guadeloupe in the West Indies received 38.1 mm of rain in one minute in 1970.