If the external DBT is 20 deg C and it is 50% RH, then it rains, what temperature is the liquid rain? I am trying to calculate the heat transfer from a surface when it is raining. I have a set of climate data which will give me external ambient DBT, RH and precipitation. So how can i predict the temperature of the rain water at ground level? My assumption is that it would be approximately equal to the wet bulb temperature. But I have no idea if this is correct. If rain is formed high in the atmosphere where the temperature is lower how can this be estimated? It is a bit strange that i cant find a straightforward answer to this question. I have spent ages goggling this and got nowhere. A reference that i can use as justification for an answer would be great.