Apologies if this has been addressed earlier. A common belief is that a cold temperature (say 0 Centigrade) feels colder when relative humidity is higher. Is there any underlying physical reason for that? As far as I can tell, the differences between dry air's and water vapor's thermal conductivity and specific heat are not very significant. At 0 Centigrade and normal pressure, at 100% relative humidity, air contains 4.8 g water vapor per cubic meter; 1 cubic meter of air is heavier than 1 kg at zero and subzero temperatures. So the variation of vapor content is less than 1% at most, so any effect on net thermal conductivity and specific heat should be negligible. Is this belief a myth, or am I missing something?