i-study.co.uk: GCSE Geography; Weather & Climate

Weather is the short term conditions of the atmosphere around us, whereas climate is the longer term average conditions of a place.

This happens as the sun heats the earth causing the air above the ground to rise.
On a sunny day clouds often form in the afternoon due to this process and can lead to heavy downpours.

This occurs when two air masses meet. The warmer air mass rises above the cooler one.
Common in the UK where there are several air masses often meeting

The Greenhouse Effect