When warm, wet air rises, it cools, and water vapor condenses out to form clouds. A cloud is made up of small drops of water or ice crystals, depending on its height and how cold is the surrounding air.
When the air cools it condenses around some dust or other particles in the air called condensation nuclei warm air can hold more moisture than cool air so when so when the warmer air is cooled and the moisture condenses it often rains more heavily
