Convectional rainfall occurs when the suns energy heats the surface of the Earth, causing water to evaporate and form water vapor. When the land heats up, it warms the air above it, causing it to expand and rise. As the air rises, it cools and condenses, forming clouds high in the atmosphere. If this process continues, rainfall will occur. This type of rainfall is widespread in tropical areas (between the Tropic of Cancer and Tropic of Capricorn) and in areas such as South East England during warm sunny spells.

The process of convectional rainfall involves four main steps: heating, rising, cooling and condensation, and precipitation. The sun heats the ground, and warm air rises. As the air rises, it cools, and water vapor condenses to form clouds. When the condensation point is reached, large cumulonimbus clouds are formed. Heavy rainstorms occur, usually including thunder and lightning due to the electrical charge created by unstable conditions.

Convectional rainfall is limited to the equatorial calm belt because the clouds carrying the water vapor are not carried away by the wind, and hence, it rains in the same place.