High Clouds (mean height 6 to 13 km):
- Cirrus: do not give precipitation.
- Cirro-cumulus: Thin, white patch; sheet or layer of cloud;
- Cirro-stratus: mainly formed of ice-crystals.
Middle Clouds (mean height 2 to 6 km.):
- Alto-cumulus: composed of super-cooled liquid droplets.
- Alto-stratus: precipitation may fall either as fine drizzle or snow.
- Nimbo-stratus: it is a rain, snow or sleet cloud; never accompanied by lightening, thunder or hail.
Low Clouds (mean height 0 to 2 km.):
- Stratus: difficult to differentiate between high fog and stratus.
- Cumulus: they dissipate at night.
- Cumulo-nimbus: These clouds are associated with heavy rainfall, thunder, lightning and hail; have flat top and a flat base; it obstructs the sun.