We’re enjoying a spate of brisk winter weather here in Stockholm (below freezing no matter how you measure it) and this morning one of my co-workers commented on how it seemed colder here than it did up North because Stockholm, being situated on the water, was more humid than the cold frozen wastes above the Arctic Circle.
My skepticism meter went off, since I’d always heard the old chestnut “It ain’t the heat, it’s the humidity” as an explanation for why some places felt hotter than others (backed up by personal experience comparing 90 F in muggy Washington DC with the same temperature in bone-dry Ankara). It seems odd to me that atmospheric moisture could affect air temperature differently depending on whether you were above or below the freezing point of water.
For the heat, it’s easy: Your body rids itself of excess heat by the evaporation of sweat. The higher the humidity, the slower your sweat evaporates, and it feels warmer. Compare dry sauna with humid sauna.
For the cold, you won’t (of course) consider evaporation, since evaporation helps your body to remove heat. But it sure feels colder when the air is humid. I don’t have any data on thermal conductivity of moist air, but remember that your body has loses heat to the surroundings, i.e. the air contacting your body. Moist air has a higher heat capacity, so you need more heat to warm it up to the same temperature, and your heat loss increases. Sort of the same effect as the wind chill (increased heat loss), but due to another physical phenomenon (heat capacity of the surrounding medium rather than heat transport by removing the heated meduim from the warm body). It may also be because dry weather is associated with high pressure and nice weather (hence, less wind), while humid weather often comes with wind. You often also lose the sun when the weather is humid, and the sun gives a little bit of warmth, even in the winter and even at high latitudes.
This is, of course, pure speculation. I haven’t checked any engineering tables nor made any measurements myself. But yeah, -10°C feels a lot colder when the humidity is high. -10°C with sunny weather and dry air is really no big deal at all. Just remember to wear good shoes.
Having lived in Luleå in mid winter my personal opinion is that “It ain’t the cold, it’s the humidity” is a mantra the people in Northern Sweden keep repeating to themselves to be able to stand the temperature.
This is anecdotal as hell, but anyway: I’ve personally experienced going outside my house in 15-18 (celcius) below freezing and just thinking “Yeah, frisk, but manageble”. Then I’ve gone downtown, close to the sea, and almost frozen my butt off in 5-8 (celcius) below freezing.
I don’t think the conductivity or heat capacity of humid air is much different when it’s cold. At low temperatures, 100% relative humidity air does not contain much water; a fraction of a percent.
I think extra humidity should always make people feel warmer, because evaporation is reduced (and there will be some whether you feel sweaty or not).
Of course, being near the water often implies having a low and distant horizon and so little protection from the wind.
I personally live 200m from the shore and I think this effect is sometimes so clear that you feel it when traveling only 20km away. It is perfectly obvious if you move 100km.
I’ve always thought that more humid air simply transfers heat both away and to the skin, so it works both ways. Now that I think of it, I guess it’s just my intuition, so no fancy tables here either.
In Central Texas, around 60 degrees F is comfortably brisk. On the humid island of Taiwan, 60 deg F (15.5 deg C) is unbearably chilly without a couple of sweaters on.
The message seems to be that this hasn’t been studied conclusively, someone affirms it anecdotally and someone suggest that the worst is actually just below freezing with 100% humidity.
And the bottom paragraph recommends polypropylene underwear. Yech. Double yech. Polypropylene which has been used just a few times stinks to high heaven, even if it’s been washed every time you’ve worn it and even if it’s fresh out of the washing machine. Besides, if it gets wet, it’s just clammy.
The only underwear that works in sub-freezing temperatures is wool. Unless you’re really sweating, like when jogging or cross-country skiing. Then you should use PP and dive directly into the shower the minute you get in.
Definitely not the case for Barcelona, which is surrounded by a ring of hills, but we’d go to bed early there just in order to give our bodyheat time to dry the freaking bedsheets.
Below freezing in Tudela (right next door to a desert that’s been used as “Arizona” in movies), broken heating, only one heater in the whole house and that one in the living room. Go to bed, snuggle in, turn around a couple of times, fall asleep.
10-15ºC in Barcelona’s high humidity, house with no heating, only one heater in the whole house and that one in the living room. Go to bed with a book, half an hour later if you turn around and touch a “fresh” spot of linen it still feels like sheet ice.
So long as we were in the respective living rooms, it didn’t make a difference. Going outside was definitely nicer in Barcelona (higher temperatures and no wind) than in Tudela (where “windy” is the default value). But every time we changed clothes or got into bed in Barcelona, Dad would remind us to “speak clean, it ain’t no more fucking difficult!”
Anecdotal- a few years ago I drove from Texas to Colorado for a vacation. The day before we left to head home, I remember walking to the hot tub in a swimsuit… it was 9 degrees out. Yes, I was cold, but it wasn’t that bad.
When we got home back in Texas and started unloading the car, it was 41 degrees and misting. I was wearing a coat, jeans, and a long-sleeve shirt… and I was shivering because it felt so cold.
The effect is certainly there, the reason for it might be elusive. Let’s put aside sub freeze point temps for a moment and concentrate on cold weather above the freeze point. 40 F in Jacksonville Florida on an overcast and humid /wet day was far more miserable then 40 F in San Antonio in a dry climate with similar overcast conditions. My guess is that the cold, but not freezing mist/ water vapor in the air collects on your skin, taking longer to heat up, while simultaneously producing the extra cooling effect of a light sweat. When this happens around the freezing point, but not below it, it can have a serious effect on the perception of the cold.
One other thing. Have you noticed how when the temperature drops down to 5-10 degrees in the autumn it feels quite chilly but when it climbs up to the same temperature in the spring it’s a nice, if not warm so at least an uncold, day?
Can’t agree with you on this. I grew up in North Dakota, and am deeply familiar with long underwear. After a couple of decades in warmer climes, I moved to Minnesota and discovered polypro long underwear. It’s warm, and wicks moisture. I never liked wool underwear, and cotton longjohns are worse than useless when wet. I’ve never noticed the stink problem you mention. My standard cold-weather inner layer is always polypro: shirt, longjohns, sock and glove liners. When it’s really cold and windy a polypro balaclava under one of Mom’s knit facemasks works wonders.
I’ve always thought it felt colder when it’s humid, but I have always wondered if that’s from a combination of not dressing as warmly as I should because the air temperature isn’t very low, and the general depressing effects of a cloudy and windy day.
Having recently moved from the California coast to the Rocky Mountains, I can also attest to the fact that 20 degrees in the Rockies can sometimes feel warmer than 50 degrees in California. One reason may be because it was usually windy where we lived near the coast, a second is that we dress more warmly living in the mountains. I could swear that it feels colder as the humidity goes up… but I have not objective way to measure that.
Anyone who has an adjustable humidifier on their home heating unit should be able to tell you:
If you set it too high, and add to much moisture to the air, you’ll always feel chillier for a given temperature. You’ll find you can’t lower the thermostat very much without an annoying chill.