Evaporation is the process of escape of water molecules from the liquid body into the atmosphere in gaseous or vapor form.
Evaporation happens at temperatures below 100 degrees also.
Evaporation happens because water molecules near the surface of water, get attracted by the gas molecules, they get sufficient energy from the temperature of the atmosphere and from the heat present inside the water molecules. They are able to get the heat required for latent heat of vaporization also. Since the latent heat is high, water does not evaporate quickly at lower temperatures.
The water evaporates as the air near the water surface is not saturated with the varpor. So the air molecules attract the water molecules. Evaporation happens, as a process of equilibrium at the water surface. It depends on the pressure of gas at the water surface. It depends on humidity and temperature.