- A front marks the boundary between two air-masses, and appears on the weather map as a line with triangles or semicircles attached.
- Cold – Cold fronts push in underneath the warmer air ahead of them, forcing the warm air upwards and making cloud and areas of rain.
- Warm – advancing warm air rises over a zone of retreating cooler air, making a cloud bank that slopes forwards from ground level upwards, often bringing prolonged steady rain.
- Occluded – a cold front overtakes a warm front, so that all that remains of the original warm air is trapped above, where it cools making dense cloud and rain.
- Stationary – a front is one which has lost its movement. Any rain clears slowly and temperature and pressure do not change much.
