I surmise that the person who asked this question was wondering why water in a room may sometimes be colder than ambient air and by how much.
For water to get cooler than ambient air requires two conditions: exposed water surface or water able to seep through a clay pot, and relatively low ambient humidity level (usually lower than 30% relative humidity). These two conditions combined enable evaporation. Now, evaporation of liquid water into water vapor necessitates input of latent energy (2257 kJ/kg), and this is at the expense of the remaining liquid water. Thus, liquid water in a room can be at a temperature lower than room temperature.
<span>By how much? There is no straight answer to this because the temperature of the remaining liquid water depends on (1) the rate of evaporation, which itself depends on the amount of surface exposure and the room humidity and temperature, (2) the amount of water remaining in the pot, and (3) the rate of reheating of the water by the ambient air. In practice, the water temperature can be lower than room temperature by several degrees Celsius. </span>
