RAIN AND SNOW
The tiny water droplets inside a cloud may bump into each other and join together to form larger droplets. If the air inside a cloud is rising, these droplets are lifted up again and join with others to form yet larger droplets. When the droplets are very large, about the size of raindrops, the rising air can no longer lift the drops back up and so they fall as rain.
The water cycle
The evaporation of water caused by sunshine makes the air moist. Moist air travelling inland may have to rise over hills and this cools it. As the rising air is cooled, clouds form and rain may fall. The rain falling on the land runs into streams, which flow into rivers. The river water eventually returns to the sea.
Seen under a microscope, snowflakes have intricate patterns.
If the air inside a cloud is very cold, snowflakes may be formed. A snowflake is formed by water vapour below freezing point condensing upon dust in the clouds. Tiny drops of water may hit the snowflakes in the cloud and freeze to ice, making the snowflakes larger.
If there is a strong current of air upwards inside a cloud, the falling pieces of ice may be lifted back up, and more ice will form on the outside. This process is repeated until, eventually, the ice is so heavy it falls to the ground as hail.
Hail can form very large balls of ice.
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