Different types of rainfall in the UK

On average, it rains one in three days in the UK. Highland areas to the west receive the most annual rainfall compared to the low-lying areas in the east. The southwest prevailing winds bring moisture from the Atlantic Ocean.

Northwest Scotland has the greatest average rainfall, with over 3,000 mm. East England receives the least, with less than 700 mm.

Types of rainfall

There are three different types of rainfall:

  • relief
  • convectional
  • frontal

Relief rainfall

Warm, moist air from the sea rises over the mountains. As it rises, the air cools and condenses, forming clouds and rain. After the mountains, the air descends and warms. This area is the rain shadow.
  1. Relief rainfall occurs when warm, moist air from the Atlantic Ocean rises up over mountains.
  2. When the warm air rises, it cools and condenses to form clouds, which brings rain.
  3. Once the air has passed over the mountains, it descends and warms.
  4. This creates drier conditions known as a rain shadow.

Convectional rainfall

The sun heats the land and the air above. The warm air rises, cools and condenses, forming clouds. Rain can then occur.
  1. Convectional rainfall usually occurs during the summer in the UK, when the sun heats the land.
  2. This creates rising pockets of warm air, known as convection currents.
  3. Warm air rises rapidly, where it starts to cool and condenses to form clouds.
  4. These clouds can be large cumulonimbus clouds.
  5. The clouds can produce heavy rainfall and thunderstorms.

Frontal rainfall

Warm air is forced to rise over cold air. Condensation forms clouds. There is heavy rain along the front.
  1. Frontal rainfall occurs when a warm front meets a cold front. The heavier cold air sinks to the ground and the warm air rises above it.
  2. When the warm air rises, it cools.
  3. The cooler air condenses and form clouds.
  4. The clouds bring heavy rain.