Rainfall is caused by air rising; as the air rises it cools and it is able to hold less water; condenstation occurs, clouds form and then precipitation falls.

Different Typs of Rainfall (different reasons air rises)

1. Relief Rainfall  - air goes towards a mountain, it is therefore forced to rise.
2. Convectional Rainfall - air heats up by contact with warm ground; it is less dense so it then rises.
3. Frontal Rainfall - at a warm front, warm air rises over cooler air. At a cold front, the cold air forces warmer air upwards.