How does the water kept in an earthen pot (mataka) become cool during summer?

Explanation

The earthen pot (or matka) has a large number of extremely small pores in its walls. Some of the water kept in the earthern pot continuously keeps seeping through these pores to the outside of the pot. This water evaporates (changes into vapour) continuously by taking the latent heat of vaporisation from the earthen pot and the remaining water. In this way, the earthen pot and remaining water lose heat and get cooled.