But it's a dry cold...

Caution: This may degrade into IMHO territory, so mods please move as appropriate.

I currently live on the coast of Caifornia, so my experiences with truely cold weather are few and far between. I will be moving to Northwest Montana in a few weeks so I will be living somewhere that has four distinct seasons… but I digress.

When I was discussing the current weather in Montana with a co-worker, and I mentioned that the temperature had recently gone up to 30 degrees F, the co-worker said, that’s not that cold… they have a “dry cold” there. A dry cold? He said that in places that have low humidity, like in the Rockies, the “sensation of coldness” is very different than if you are in a high humidity area, like the east coast. He seemed to know what he was talking about, but since I had never heard of it I quickly changed the subject.

So my question to the teeming masses is…

Is there an equivalent cold weather phenomena to “it’s a dry heat” that you often hear about from people that live in places like Arizona? Or is my co-worker full of crapola…

Yep it’s true.

30 degree air, has air at 30 degrees and dispersed water at 30 degrees. Humidity is the portion of water mixed into the air.The water portion has a higher specific heat, and sucks heat out of you faster. More water by percentage; the faster the heat sucking goes.

I am one of the Colorado folks people make fun of who wear shorts on still days until it gets under 10 degrees. But with dry air, and no wind(and with my excess fat) I am perfectly comfortable generating as much heat as the air is taking away when it’s around 30.

High humidity amplifies the feeling of cold or heat. As the old saying goes, “The coldest winter I ever spent was a summer in San Francisco.”

And the coldest winter I can remember was when I was stationed at Ft. Benning GA.
30deg’s and I was freezing!
Its 30 deg here today and it feel like summer! Opp’s that was 2 hours ago. Its 42 now, time to dig out the air conditioner:D

So people who live in high humidity areas get a double whammy? Colder feeling winters and hotter feeling summers! That doesn’t seem fair.

Low humidity has it’s negatives too.

Places with low humidity cool down really fast after the sun sets. In a places with 85% humidity on a 75 degree day it can be nice and 65 ish until midnight.

That 75 degree day in the desert or near desert might be 40 by midnight because there is no water in the air to hold heat and slowly readiate it.(hehe like I said I don’t mind the cold and dry, but lots of people seem to from my experiences in Moab)

I would also point out that this dry vs. humid cold effect really only takes place over a fairly narrow band of temperatures. Once you get to actually cold temperatures, say -30C and below, the effects of humidity are nearly non-existent because even 100% relative humidity at -30C is almost 0% absolute humidity. When people say, as they are wont to, of -45 on the prairies, “but it’s a dry cold” what they are doing is making a joke.

Unfair, but true. I grew up in Montana, and I never knew cold 'til I felt the wind coming off the lake in Chicago in the winter. Sweet cracker sandwich, it was cold!

Going to school in Chicago is the only time I’ve felt scared to leave the house, and that’s counting -25 weather up here.

so true. i grew up in northern canada where winter temps of -45c to -48c where normal. When I moved to Kelowna (about 1000 miles south to drive) where it barely got below freezing I couldn’t believe how cold it was. It was near a lake so the humidly was high. I quickly lost my smirk!

Yeah, this is what is leaving me scratching my head. Even at 0C, the absolute humidity difference between 0% relative humidity and 100% relative humidity is only4.3g/m^3. I can’t imagine that causing the tremendous effect on heat transfer rates that many people here seem to be claiming, but I haven’t done the math.

The Weather Network here in Canada has a faq calling this a myth. Specifically:

I think that’s the answer - Wind chill. Less wind in drier climate.

I’ve lived in very cold places, and now live in SF. I’m colder here, and more often, than I’ve been anywhere.

Wow! I had no idea. So “it’s a dry cold” is a myth? Funny how everyone I talk to seems to believe that it’s true…

Just because lots of people believe it doesn’t make it true.

Here’s another cite. This time from Environment Canada, here:

I also found a blog entry from a reporter who described his conversation with an EC scientist in which that scientist explained that testing in cold chambers proved that the dry cold theory isn’t true. That’s here.

I admit that I have not found a study available online, just these circumstantial cites.

I grew up in central British Columbia where it can get down to -40C. I always thought it was damn cold.

Later, I made some friends who had moved to central BC from the Lower Mainland (Vancouver) which is a very mild and humid coastal region of the province. Even in mid-winter temperatures rarely dropped below freezing. But they would say, “Yea, but it’s a damp cold, it’s so humid. The cold goes right to your bones. It’s way worse than what you get up here.” My response was always, “Wow, really?”

Well let me tell you, after having lived on the coast for a couple years now, it’s a myth. Winters on the coast are a cakewalk. Sure, it’s damp and rainy, but people are still riding their scooters. People are still hanging out at outside cafes sucking down their lattes. Try that crap in -40C, Popsicle Pete.

I have never heard of a dry cold. Dry heat, yes, but never dry cold.

If asked, I would have guessed that a dry cold makes you feel colder, due to quicker evaporation.

One thing to consider.

If your clothes get damp in a “wet” cold, they feel damn cold and clammy when you put them on and they won’t dry out on their own.

Dry materials are better insulators than damp or wet ones.

If you are all bundled up you tend to sweat. If they air is dry that moisture has somewhere else to go. If the humidity is high, all you are doing is slowly dampening your clothes.

Modern synthetic and breathable clothing are much better than the old days of cotton and scratchy wool.

I’ll go along with the dry sunny day explanation. But there is another factor. If you wake up and the thermometer reads 0C you will dress differently than when it reads -25 and you may well feel colder in the first one.

The coldest I ever was when I spent six weeks between lated June and early August in Sydney. The reason was that there is no central heat and every room in every house has an “air brick”, a porous brick that Australians seems to believe you will suffocate without. Someone told me when I arrived I would feel warm outside and cold inside and so it proved. The coldest day there was a high of 8C (and they said it was only the second day in the 20th century that the temperature didn’t get above 10.

That’s it in a nutshell. People in the PNW tend to underdress, and hang out in the cold and wet world. No way was Seattle colder than Chicago, but in Chicago your bundled up and protected.