The amount of water vapor in saturated air varies with temperature.
As saturated air cools,
condensation temporarily increases, removing water vapor until a new
balance is reached. As saturated air heats up, it becomes under saturated. However,
evaporation can add water vapor until the air is again saturated.
Step-by-step explanation:
Water vapour is the gaseous form of air which is mixed with the normal atmospheric air. The amount of water vapour that the air can hold is directly proportional to the temperature of air. As the air heats up, the capacity of air to contain more water vapour increases and so the air becomes under condensed. Then the increase in temperature also increases the rate of evaporation which again adds more water vapour from the natural water bodies to air, to make it saturated again.
As the air cools, the air becomes over saturated, which can't hold any more water vapour, so the water vapour condense on small dust particles which fall on earth as rain.