Precipitation associated with a thunderstorm is often torrential and of a short duration. The release of precipitation is very sudden and the rain drops are large-sized, so that it is called the thunder-shower.
Torrential rains from the cumulonimbus are produced because of two factors: (1) vigorous convectional currents are produced in a thunderstorm; (2) specific humidity is high because the thunderstorms develop in summer when the temperatures are very high.
The cellular structure of a thunderstorm largely determines the nature of rainfall. Maximum amount of precipitation is recorded at the centre of each cell from which it decreases outward.
In these convective cells the duration of rainfall varies from a few minutes to more than an hour.