Dear student, â—Humidity occurs due to the presence of water vapour in air. As water vapour is considered as an important green house gases which plays an important role in deciding the temperature of a place by trapping the outgoing radiation and then moderate the climate of a place. Water vapour are responsible for the formation of clouds and the subsequent precipitation. The presence of water vapour in air in the form of humidity controls the long wave radiation balance of the atmosphere etc. â—Regards