Precipitation

Any moisture that falls to the ground from the air is called precipitation. It includes rain, snow and sleet.

Warm air rises and carries water vapour with it. Once the vapour hits the colder air high in the atmosphere it condenses and forms droplets of water around tiny bits of dust. These droplets merge together to form larger drops which eventually fall as rain.

When the air is very cold the water vapour will turn to ice crystals. These join together to form unique hexagonal snow flakes. Most snow turns to rain as it falls and meets the warmer air but when the air near to the ground is cold enough it will remain as snow.

When the snow flakes fall and meet warmer air that is not enough to fully melt them, they only partially melt and you are left with a mixture of snow and rain caled sleet.

The Earth's water is constantly being recycled as it rises to the atmosphere as water vapour and falls as rain. This is called the water cycle.