how do the misters outside of hotels cool the air?

Answer 1

Mist is made up of water in very small droplets. When water evaporates it takes energy. Evaporation is an endothermic process. When the "liquid mist" turns to water vapor , the energy needed is supplied by the surrounding air. Heat is taken in by the water and the surrounding air is cooled. The misting process may also remove dust particles and pollutions from the air. The degree of cooling depends upon many factors, like relative humidity, etc.
Hotels may use misting systems to lower the temperature and improve the air around their buildings.

read more see:

http://www.fogco.com/cooling.asp
http://en.wikipedia.org/wiki/Endothermic
http://en.wikipedia.org/wiki/Endothermic

Answer 2

Same was as the Mrs.