Humidity is the amount of water vapor present in the air. Humidity indicates the likelihood of precipitation, dew, or fog to be present. Humidity is one of the fundamental abiotic factors that defines any habitat (the tundra, wetlands, and the desert are a few examples), and is a determinant of which animals and plants can thrive in a given environment. It affects the energy budget and thereby influences temperatures in two major ways. First, water vapor in the atmosphere contains "latent" energy. During transpiration or evaporation, this latent heat is removed from the surface liquid, cooling the earth's surface. This is the biggest non-radiative cooling effect at the surface.