This is a very logical question. Clouds are formed from moisture that evaporates from the earth, and most of the surface of our planet is covered by the salty seas. At some stage in the weathery water cyc1e the salt is sifted out and the rain that falls is the earth's freshest water. The water cyc1e is powered by the beaming sun. As the earth rotates, its warm rays evaporate moisture from every watery surface. The moisture becomes gaseous vapor that condenses into misty cloud droplets. The cloudy moisture condenses and precipitates rain and snow, hail and sleet upon the land and sea. Life on earth depends on this precipitation, and it is adapted to this supply of fresh, salt free water. If the clouds suddenly started dousing salty water, most of the earth's plants and the animals that depend upon them would perish. Every year some 350 billion tons of rain water rain down around the world, and some 80,000 cubic miles of moisture are evaporated from the sea to contribute to this ...
When water evaporates from the oceans, it does so as single water molecules. The molecules whose vapour pressure can launch them into the air will manage to evaporate, even well below 100 degrees C. The salt ions have strong electrostatic attractions to the polar (partially split-charged at the ends) water molecules around them. Single water molecules leaving the surface just. don't have enough electrostatic pull to take the ions with them away from all the other water molecules surrounding the ion.