Weather is the source of water in a watershed. Precipitation, usually in the form of rain, falls to the ground and either evaporates, soaks into the ground or flows over the land and into nearby bays, lakes, rivers and creeks. Sunlight, wind and temperature affect this process. High temperatures, abundant sunlight, and strong winds can speed evaporation. Water is also affected by the change of seasons. The amount of precipitation that falls often varies from season to season, as well as the water requirements of plants and animals.