The water molecule is asymmetrical, with oxygen atom on one side and hydrogen atoms on the other. Weak electrostatic forces hold the liquid water molecules together, making water difficult to evaporate. The same weak electrostatic forces must be overcome to cause water molecules to align in the rigid crystalline structure of ice. Therefore, water exists as a liquid through a wide range of typical earth surface conditions. About 600 calories of heat energy are required to evaporate 1 gram of water.
Evaporation serves as a vital cooling process.
Because the change of state of water involves huge transfers of latent energy, it is crucial to assess the water content of the atmosphere to understand its energetic potential. Moist air carries a great quantity of latent energy that is absent from dry air. This helps power thunderstorms, tornadoes, hurricanes, etc. Therefore, maritime climates are much different from continental climates. Water is also a coolant.