Do clouds shrink when it rains?

A cloud loses mass when the water vapour that the cloud consists of condenses into ever larger drops that finally fall to the ground as rain. But usually, the rising flow of warm, moist air that produced the cloud in the first place will continue and constantly supply the cloud with new mass. In other words, even though the cloud gives off lots of water in the shape of rain, it also receives new water from the moist air, so in total, it does not get any smaller.

Major clouds such as the cumulonimbus thundercloud might continue to rain, after the supply of water vapour from below has stopped, and then the cloud will naturally become ever smaller. Clouds lose mass, when it rains, but rising air supplies new mass. So, the clouds do not become any smaller.