COOLING EFFECTS OF EVAPORATION

 Why does a desert cooler cool better on a hot dry day?

When a desert cooler is working water is continuously sprinkled inside it. In hot and dry days that water  evaporate faster due to high temperature and low humidity. As a result of evaporation of water, (sprinkled inside the cooler), air inside is cooled due to absorption of heat. This cold air is sent out to the room with the help of fan in the cooler. So cooling effect will be more on hot dry day.