Earthen vessels can help maintain the temperature of water inside by utilizing evaporation from their porous surfaces. When water in an earthen pot is cooler than the surrounding environment, the evaporation process cools the outer surface, which indirectly helps keep the water temperature stable. Unlike metal vessels, which conduct heat and can warm the water, earthenware does not allow heat to flow from outside to inside effectively. The discussion highlights that while earthenware may seem structurally inferior, its ability to cool water through evaporation makes it a practical choice in areas without electricity. Overall, earthen vessels serve as a simple and effective means of temperature regulation for water.