*Thoughts on staying warm when it is EXTREMELY cold*
By: Fred Heiser
01 December 2003

I hate cold. I was born and raised in northern Michigan. For three months of the year you could expect bitter, subzero cold, the kind of cold that froze the hair in your nose and killed the battery in your car, froze even your buried pipes and left you with astronomical heating bills. Cold that led the unprepared very quickly to shivering, frostbite, hypothermia and sometimes death.

Every year came a new set of stories of people who got their cars stuck in a snowdrift somewhere and froze to death and of skiers and snowmobilers who got careless and lost extremities to frostbite. Sometimes the cold was coupled with high winds and snow. The worst I ever experienced was 43 below zero with a wind chill of 70 below.

My mother did not know how to stay warm. When it got cold she bundled me up in so much clothing I looked roughly like a sphere with thick stubby projections for my limbs and head. I could hardly move. Not a good idea and it got you teased at school.

I spent a lot of time studying how to stay warm. The obvious solution is to move south, one reason I eventually found myself in California.

Staying warm is a matter of assisting your body’s natural defenses to cold. When it gets cold your body does a number of things to protect itself. Your metabolism gets kicked up a notch to generate heat. Circulation is directed away from the surface of your skin, your layers of insulating fat and your extremities in order to keep the vital organs and brain warm. In severe cold this can lead to frostbite as your body literally sacrifices your fingers, nose and toes for the sake of your core. The skin itself tightens up to close off pores to cut evaporative cooling (goose bumps) and in men the external reproductive organs retract and shrivel. Sinuses contract so as to squeeze more heat out of air before it is exhaled.

As it gets colder, if your metabolism cannot keep up with the heat loss you begin to shiver, a very efficient method of generating heat quickly. This is a sign of incipient hypothermia. Your blood gets thicker as the core temperature drops. The shivering gets worse and worse as you get colder and colder and you become confused as brain temperature begins to drop. Keep it up for long enough and you become exhausted and want to sleep. You start to lapse into deeper and deeper hypothermic states. Your metabolism slows to a crawl and then you die.

Ironically, this deep hypothermic state is what allows a drowning victim to be resuscitated after up to a half hour of submersion in freezing water. Your body functions slow to a crawl and you don’t need much oxygen to survive if your systems have all but shut down

The first steps in cold protection are taken long before you set foot outside. Good cardiovascular conditioning is an important factor. Circulation of blood is how the body transfers heat from one part of the body to another. Cardiovascular conditioning improves the ability of your body to pump blood where it is needed most with the least effort and when your blood thickens from the cold, this is important. Good condition also means you breath less. A tremendous amount of heat is lost through breathing due to evaporation in the lungs. (In fact for many animals this is the ONLY means of evaporative heat loss.)

If you have serious sinus congestion, take a decongestant. Sinuses serve to preheat air before it gets to the lungs. When the very warm air from the lungs air is exhaled, some of this heat and moisture is recovered by the sinuses. Clogged sinuses prevent this heat transfer from taking place. And heavy mouth breathing is to be avoided at all costs in severe cold. It is VERY effective at getting rid of heat (That’s why a dog pants when it is warm.) and can be hard on your lungs.

Keep your body stoked with fuel. You want a mixture of high calorie carbohydrates and fats. Carbs give your body instant energy while the fats stay around for long term energy. Stay hydrated. Dehydration is a serious problem in cold weather. The low humidity sucks the water right out of you. and adds to the deleterious effects of hypothermia. A thirsty man is tempted to eat snow and in a potentially hypothermic situation you don’t want to be shoveling ice right into your stomach. Better to tank up on hot cocoa before you leave. Coffee is okay most of the time but can act as a diuretic and can add to winter dehydration. (Besides, when you urinate you lose a lot of heat.)

Avoid alcohol like the plague in extreme cold. It gives your extremities and skin a nice warm flush by enhancing circulation to them, just exactly the opposite of what your body is trying desperately to do. Alcohol also adds to the impaired judgment caused by hypothermia, slows your metabolism down and exacerbates any feelings of drowsiness. Once you’ve reached a place of warmth and safety a little brandy to improve circulation to those cold extremities isn’t out of line. I kind of like hot spiced apple wine myself.

If you have time, try to acclimate yourself to the cold. Go outside and putter around the yard, make a snowman and engage in some target practice. Stay outside until you are colder than is comfortable and then go back in. Start with the very first autumn frosts and stick with it until March goes out like a lamb. Do this every day and in a matter of time you’ll discover your body is much more tolerant to the cold. When he was preparing for a stunt of being chained up and dropped through a hole in the ice in the Detroit River, Harry Houdini practiced by soaking in a bathtub full of ice water. Came in real handy because after he got himself unchained, he couldn’t find the hole right away and he had to subsist on pockets of air trapped under the ice sheet he found his way out. An ordinary person would have vapor locked within a minute and died soon after. You don’t have to go this far but it shows just how cold tolerant the human body can potentially get.

And one more thing. Don’t shave. Even if you don’t want to grow a beard, leave the 5 o’clock shadow there until after you’re out of the cold. Shaving takes off the outer layers of skin cells along with the hair and makes the skin more vulnerable to frostbite.

Now that your body is prepared for the cold, what kind of clothes to wear? You want your clothes loose and layered. Looseness allows your blood to circulate freely and gives you freedom of movement. Layered makes it easy to adjust how much insulation you are wearing according to your level of activity. The one thing all insulating materials have in common is that they are degraded by moisture. The last thing you want to do is work up a sweat from hard work. The moisture evaporates which cools you off (not good in a cold survival situation), then in very cold weather it recondenses in the outer layers of your insulation.

Everybody sweats all the time over their entire body. You body tries very hard to keep a thin boundary layer of warm moist air over all your skin. This layer is constantly drifting off and being recreated through insensible perspiration. Little by little your outer garment can lose its insulative value from recondensation of this moisture. In dry weather, if your outer garment is porous most of this water vapor will pass right through. However you don’t want to accelerate the process by dumping a load of sweat into the system, especially if it is cold and WET. Plus heavy sweat can ruin your inner layer of insulation by soaking it. This is most obvious in people wearing cotton socks which can get drenched. Layering allows you to open up and/or remove layers of insulation when you are working hard and generating heat to keep you from sweating excessively and ruining your insulation. Put the outer layers back on as you cool off.

Don’t forget that each layer needs to be loose enough not to compress the layers beneath or to bind your freedom of movement. Most cold weather aficionados start out with a layer of polypropylene for their undergarment. This has the ability to wick water off your body so you are no longer in contact with it. They make polypro socks too, as liners. Over this you apply as many layers as you think you’ll need and then one more for safety. Thermal underwear, casual clothes, insulated vest, insulated bib overalls, a parka, rain gear, etc. Don’t make the mistake of covering your torso with 3 inches of insulation and just a pair of pants for your legs. If it is that cold, your bottom half needs the insulation as much as the top half.

The one fabric to avoid is cotton. Nothing is better than cotton for absorbing water and holding on to it. Once wet it has NEGATIVE insulating value because it sticks that cold water right too you. If you are caught in a heavy cold rain in a cotton t-shirt and denim pants you may soon find that you’d be warmer nude. Cotton is great for dry conditions however and a cotton flannel or sweat shirt isn’t bad a choice for casual winter wear and if lined with a synthetic it makes a good light jacket.

Different types of insulation each have their advantages. Down is the lightest, compresses best and insulates best. It is also the most vulnerable to moisture. Even a little water zeros out down’s insulative value. Synthetics like Polarguard and Hollofill are heavier not quite as compressible and have slightly less dry insulative value. However if they get wet they still retain some of their insulative value, about 30% after you’ve wrung them out. Doesn’t sound like much but if you’ve just taken a spill in subfreezing weather it can mean life or and death.

If you go for down, goose down is better than duck down (unless its from the Eider duck with is without equal in warmth per weight). Down from cold climates is better than from farms where it is warm. Pure down is better than a down/feather mixture. Down equipment should be washed as little as possible and then preferably only in cold water. Detergent takes away oils that are essential for down’s high insulation factor.

Wool is a fantastic wet weather insulator. Wrung out it still retains 70% of its insulative value. It is your best choice when it comes to casual clothes, socks, shirts and pants. A wool sweater is a choice for immediately over your casual clothes and under your parka. Wool fleece is very good for outer wear. Wool is not as compressible and weighs more.

Even if it isn’t waterproof your outer layer needs to be windproof. Gortex, a synthetic with extremely fine pores that allows water vapor through but not liquid water is a very useful combination of the two. A coating of Scotch Guard on nylon works too.

Extremities require special protection. Mittens are the warmest for the hands. They make “shooting mitts” either with slits in them or a separate trigger finger so you can get your fingers out to work a trigger and do detail work. I like to wear a pair of thin, form fitting cotton/nylon white gloves underneath as an additional layer. (I’ve had my fingers freeze to bare metal before and it is not fun). If you wear gloves I recommend mil style, with a leather outer and a wool inner. Avoid tight constrictions around the wrist. I also have a pair of leather gloves lined with Thinsulate (another synthetic insulation) that give me warmth with minimal bulk.

Your head is another extremity to protect. 40% of your body’s total heat loss is from the head. Ears nose and cheeks are exceptionally vulnerable to frostbite. Your brain must be kept warm at all costs. Baldies are at a distinct disadvantage here as hair is very good insulation. So are the clean shaven and women.) Your neck can be covered with a turtleneck or a scarf. A balaclava hat is a knit hat that can be pulled down over your face to your throat. Don’t get one that doesn’t have an opening for nose and mouth in addition to eyes, They may look warm but in really cold weather you create blobs of ice when you exhale.

Any good parka will have a windproof insulated hood with a “stove pipe” neck that can be buttoned up to your chin and a drawstring to cinch the hood down for minimal facial exposure. And even that area can be protected by a ski mask. However if you have layered properly you don’t need an insulated, fur lined parka except under Arctic conditions. You just need an outer windproof shell to cover the thick sweater, the wool casual clothes and the insulated undergarments. The longer the outer layer the better, all the way down to your knees is good.

The folks who manufacture space blankets also make a poncho out of the material. Very useful as an improvised outer shell or stand alone rain gear.

Your feet are the second largest source of heat loss. They are in constant contact with the cold ground and sweat profusely even when cold. In coldest of weather you should wear a thin liner sock, a plastic bread wrapper a thick wool sock and then an insulated winter boot. I grew up with Sorrel boots with removable felt liners in Michigan. I came to know and love Mickey Mouse boots through the courtesy of Uncle Sam but a 30 year old pair of well waterproofed (and very heavy!) leather hiking boots have seen most of my winter action. (The Vibram soles are held in place by screws. Had to replace the original steel screws recently with brass because of rust!) If the snow is deep and your boots are not, a pair of gaiters is indispensable in keeping the stuff out of your socks. A gaiter is a fabric tube that covers everything from your shoes/boots up to your calf. A strap slips under your boot just ahead of the heel to keep it from riding up.

Okay, what’s this about a bread wrapper? It’s like this. Your boots should be fairly waterproof, otherwise water from snow will seep in and freeze your feet. However your feet are always sweating. In a completely sealed environment it won’t be long before your socks start to get soaked. The solution is to trap the water next to your feet with a vapor barrier. Your polypro liner gets soaked with sweat but your wool insulation stays dry. I wouldn’t recommend this for months at a time or you’ll get trench foot but for short outing it works fine. It also means that you only need one pair of wool socks for a trip of several days since they never get wet or dirty.

Vapor barrier insulation is useful for more than your feet. I have an aluminized plastic shirt that I can wear as a stand alone rain garment or as a vapor barrier under my layers of outer insulation. (You can get vapor barrier pants too.) It prevents evaporated sweat from getting into my outerwear and ruining the insulation. This also means my outer shell can now be waterproof, in case of rain or an encounter with wet snow. Additionally, this particular vapor barrier is also heat reflective. Not as good as a space blanket but still pretty good. The down side is that it starts to get clammy inside. I can get rid of the clamminess by opening everything up to vent. In a true survival situation I’d put up with the clamminess.

I also have a couple of aluminized Mylar emergency sleeping sacks. They weigh 2 ounces, are waterproof, windproof, 90% efficient in reflecting body heat. In moderate temperatures they will keep you warm all by themselves. In very cold weather they make dandy sleeping bag liners. You can also wear a space blanket poncho as your vapor barrier or roll yourself up like a cigarette in a regular space blanket.

In a pinch, bread bags work for the feet. Trash bags work well for the rest of you. One for your upper body with holes in it for your head and arms and another for your lower body when you crawl into the sleeping bag. If you have the ones with cinch straps built in and you are short enough, you can cinch them up and tie them together. You’ll need to take off your pants when you go to bed this way or they’ll be soaked in the morning. You’ll wake up feeling clammy but warm. Most importantly there won’t be any condensate in your bag’s insulation.

Your tent should be low in profile. Hot air rises while sleeping people don’t. Low also means less of a target for wind. It needs to have a waterproof floor, preferably a bathtub design. The rain fly should cover the tent almost like a second wall. I like to take a full length Thermolite pad with me, the thickest one they have (2.25 inches inflated!) both for the insulation and the comfort. Unlike other inflatable pads, if you puncture it or it leaks, you still have a foam pad to sleep on, just not as thick. If I couldn’t take that, then I’d go with a full length Ensolite pad which is a very efficient closed cell foam material. A ½ inch of closed cell foam can’t compete with a 2 ¼ inch thermolite pad in warmth or comfort but it is lighter and packs in about the same size roll.

Be extremely cautious about taking any kind of open flame or heating device into a tent. Nylon melts easily. Burn easily too. I wouldn’t do it unless I was desperate. They make little hand warmer thingies that are useful for warming ones hands but are useless for anything more.

One last thing. In extreme cold try to have a friendly partner with you. Two bodies heat a tent or zipped together sleeping bags twice as well as one. Your partner doesn’t always need to be human either. Two of my favorite pieces of arctic survival gear are a Labrador retriever mix and a Swiss mountain dog.
Fred Heiser

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