How is the convectional rainfall caused?

The two factors necessary to cause convectional rainfall are intense heating of the surface and abundant supply of moisture. Due to intense heating of the surface, the surface air gets heated and expands and rises up conventionally holding moisture. It is thereby cooled adiabatically and its temperature falls below the dew point, forming Cumulonimbus cloud, which gives heavy rains. Such rainfall is called convectional rainfall.