Abstract: A weather instrument for directly indicating dew point temperature of a given atmosphere. A sensing element responsive to relative humidity is connected to a first cam which interacts with a second cam for producing a continuous angular output corresponding to a predetermined function of the relative humidity (RH) of the ambient atmosphere. To the second cam is connected a sensing element responsive to ambient temperature (T) for producing a continuous angular output so as to directly indicate the dew point temperature (T.sub.D) of the ambient atmosphere according to the relationship T.sub.D =T+(a) log RH, "a" being a constant.