During summer days, water kept in an earthen pot (pitcher) becomes cool because of the phenomenon of :
An earthen pot has a large number of extremely small pores on its wall. Some of the water continuously keeps seeping through these pores. This water evaporates continuously and takes the latent heat required for vaporization from the earthen pot and the remaining water. In this way, the remaining water loses heat and gets cooled.
Lakhmir Chemistry (2020, 2021)