How does humidity affect the cold?

I’ve heard that the high humidity of this area of Texas makes the winters feel colder than they really are, just as it makes the summers feel hotter. This weekend, I drove north so I could see some real snow. I visited the Palisades near Sioux Falls, South Dakota. The weather history says it was about 15 degrees Fahrenheit while I was there, but it didn’t feel that cold. I’d compare it to 30 or so here. It seems to me that cold temperatures do feel colder here than other places. Now I know why the humidity makes the heat more intense. How does it affect the cold?

What was the relative humidity in each location at the time? Cold air holds a lot less moisture than warm air, which is why most furnaces have the option to install a humidifier. The otherwise natural cold air doesn’t have the same humidity.

I ask that as an aside, because in really cold weather, I’ve never really noticed a difference in humidity affecting my own subjective feel. A light breeze can change things drastically, though.

Ya know, looking at it, it was a bit closer than I thought. It was 21 degrees here with 71% humidity. It was 16 there with 76% humidity. That’s probably fairly close in absolute humidity. I didn’t realize it was that cold here today. It certainly felt colder here though, even in the somewhat heated shop.

High relative humidity at low temperatures does feel colder though, due to the conduction of heat away from the body (water is a good heat sink).

I don’t think the effect has been calculated the way windchill and heat index have been though.

Except for the fact that, all else being equal, dry air has slightly higher thermal conductivity than humid air. (Most people believe the opposite is true.)