Why clouds won’t fall down even though they are heavier than air..?

Answer:

Weight is not the only one factor which determines whether  a object floats or sinks in a fluid(Air is also a Fluid).We have to consider it’s density.where we need to consider it’s volume also.Depending on densities we can say whether it floats or sinks.If the density is more than that of other it will sink if density is less than that of other it will float and vice versa.

In our present case even if clouds are heavier their densities less compared to that of air.That’s why they float in air.Here we should keep in mind that density of air doesn’t remain constant.So at some stage they come into equilibrium that is where they floats.

When it  come to raining clouds become denser.So it come to lower heights compared to initial height.As we know that temperature decreases as we go high from earth(up to some height later it increases).So temperature of clouds come down.Thus raining occurs at that place.