When it is raining or snowing the relative humidity is usually 100. This means the air holds all the water vapor it can hold at the given temperature. The water vapor comes from large bodies of water such as oceans, seas, or lakes. If the air containing the water vapor is cooled enough as it moves over land, the precipitation will fall. Air movement caused by differences in air temperature is called wind.
Wind is important to living things.
It moves air causing precipitation, spreads pollen, seeds and spores of many plants. It causes evaporation of water from soil. It can blow away valuable top soil from land. Light is another physical condition of the environment that is very important to all living things. The amount of light and how long it is present is very important to living things.