Re: Relationship between humidity and body feelings of cold and warmth

Date: Tue Mar 16 09:40:41 1999
Posted By: Jason Goodman, Graduate Student, Massachusetts Institute of Technology
Area of science: Other
ID: 921087534.Ot

Message:

I don't think there's a definite answer to this question, but I have some ideas.

First, a few clarifications about humidity.

I would expect that higher humidity would make one feel warmer, not colder. This is because when water evaporates off your skin, it takes heat with it. This "latent heat loss" helps keep you cool on hot days, but should also make you colder on cold, dry days. However, if it's humid enough to actually form condensed water (fog or rain), any water which gets into your clothing will allow heat to be carried through the insulation by thermal conduction, making you colder.
Weathermen generally report the "relative humidity". This is the ratio of actual water vapor in the air to the total amount possible. But the total amount possible increases radically with temperature -- it doubles for about every 6 degrees C. And in situations where the air leaving your skin has been warmed to a constant temperature by your body, the absolute humidity is important. So even though Oakland has a lower relative humidity than Cleveland, if Oakland is warmer, it could have higher absolute humidity.

Notice though that while either fact #1 or #2 alone could explain why Oakland feels colder than Cleveland, both of them together negate each other. I actually feel that for temperatures more than 20 degrees from body temperature, the absolute humidity is so low as to make humidity effects unimportant -- except that if you're actually wet, you'll feel much colder.

A much more important factor in feeling cold is windspeed. Is Oakland generally windier than Cleveland was while you were visiting?

Finally, you mentioned that "Dressing properly, I felt more comfortable outside in Cleveland". If you dressed more warmly in Cleveland than you tend to do in Oakland, that would make a world of difference. I know that while I was an oceanographic expedition to the Labrador Sea, I dressed very warmly while working outside (because I knew it would be unusually cold) and ended up overheated a fair bit of the time.

Finally, there are lots of physiological and psychological factors involved in how people feel temperature. Duration is important (you probably didn't spend much time standing around outside in Cleveland); people notice temperature changes more than absolute temperature change (people in Cleveland might keep their thermostats set lower indoors), and how you feel depends on your expectations (you expect Cleveland to be one step away from Antarctica and are surprised when it isn't.)

I realize this has been a long response without a definite conclusion, but the problem with human perception is that there are way too many things to consider.

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