Why do desert coolers are more effective in summer than rainy season??

Question

Why do desert coolers are more effective in summer than rainy season??

Answer 1

because they cool when there is low moisture in the air. by putting cold moisture in the air.

and when its raining.. theirs moisture in the air already so it can not be saturated with cold moisture,

and they are refered to as swamp coolers.  

btw as reading your question the 1st time around it read as if you were talking about cake and pie selling better in the summer than in the rainy season.

Answer 2

Mel gave you the correct answer. The interesting fact about water is that is has to take energy in form of heat in order to go from fluid to gas. This is why actually we sweat. But if the air is already 100 saturated with moisture, as it is when there is fog, there is no more evaporation hence no cooling effect.

The same happens when snow or ice is melting: it needs to take energy in form of heat.

But when water goes the other way; from water to ice or from gas to fluid, it has to give away energy in form of heat.

This is why you can see frost rim on the trees early a winter morning. The moisture in the air cannot freeze because the droplets are so little that they have nearly no mass. But when they meet anything with a mass, like the branches of a tree, they give away heat and freeze immediately.