Summary

Seawater evaporates naturally. This process is greatly accelerated under the influence of the sun. Some of the gaseous water vapour falls back into the sea as liquid rain. Another part remains in the atmosphere and is displaced by air currents as gaseous water vapour, or as liquid condensation in the form of clouds.

If the water vapour is over land then the airflow may collide with a colder airflow or hills/mountains. This will cause the airflow to rise with the water vapour, thereby cooling it. Cold air can contain less water vapour than warm air, so in the rising air, the water vapour will condense into water droplets. These then fall down as precipitation under the influence of gravity.