Question: what happens to all the clouds that do not rain

Ian Cade answered on 17 Nov 2014:

They either evaporate and disappear… or combine with other small clouds/absorb more water vapour… and then rain.

The clear sky is usually filled with quite a lot of water vapour, really not much less than a cloud. It just takes a small change in pressure or temperature to get the water vapour to condense into droplets and form clouds (or for clouds to evaporate).

You can see this happening at home… just look carefully at the steam coming out of your kettle (taking care not to burn yourself!)… there should be a small region just above the spout and below the visible steam where the air looks clear (its not that there is no water in that region, its just that its too hot. After it cools a little the water condenses to form steam)