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I'm going on a campout this weekend and the temperature isn't supposed to rise above 0° Fahrenheit the entire time. I've been in subzero weather before and I didn't last long, even with plenty of insulation. What can I do differently this time?

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possible duplicate of Keeping warm in an emergency –  Hartley Brody Jan 24 '12 at 21:06
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Not necessarily a duplicate: Emergency means that you weren't prepared for the situation. Here, the low temperatures are already expected. –  Lagerbaer Jan 24 '12 at 21:08
    
it's pretty similar to What do I do to prevent and treat frostbite? –  mendota Jan 24 '12 at 21:13
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I think this is a good, separate question. –  xpda Jan 24 '12 at 21:24
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Please specify the units: do you mean below 0°C or below 0°F? It's a big difference! –  nibot Feb 4 '12 at 0:44
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11 Answers 11

up vote 16 down vote accepted
  1. Keep active.
  2. Bring a good hat. While your body can reduce blood flow to fingers and toes to prevent the core from getting cold, for obvious reasons it doesn't want to reduce blood flow to your head. Thus, it's important to keep your head warm.
  3. Eat sufficiently. Your body needs a lot of energy to stay warm. Don't deny it that energy. Mix food with readily available energy (simple carbohydrates: sugar. Chocolate is GREAT for this purpose) and food with slow-but-long-burning energy (fat. My outdoor club's former president mixes quite a lot of butter into his dinner, which he claims helps him stay warm throughout the night)
  4. Before you go to bed, run a few circles around the campsite to get warm. It is much easier to keep warm inside a sleeping bag than it is to get warm inside a sleeping bag.
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I'd add to #4 not to run so much that you break a sweat, as wet and cold don't mix well. –  chesles Jan 24 '12 at 21:35
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You should add a note about a sleeping mat under the sleeping bag to help prevent heat loss due to convection. That makes a HUGE difference. –  justnS Jan 25 '12 at 0:16
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I thought using a sleeping mat/sleeping pad was something obvious, even just for comfort: Hard ground vs. soft mat –  Lagerbaer Jan 25 '12 at 0:24
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@Different55 Fair enough. But if it's cold then you need good insulation from the ground. For extra warmth, you can put a foam pad under an inflatable thermarest. –  Lagerbaer Jan 25 '12 at 22:24
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"for obvious reasons it doesn't want to reduce blood flow to your head" - that's a clear nonsense. I have my blood flow to my head reduced many times when some nice women is around :-) For obvious reasons :-) –  Tomas Jan 28 '12 at 0:26
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There are two important keys to keeping warm in sub-zero temperatures, keeping dry and dressing in layers.

Getting wet by any means, including sweat will make you miserably uncomfortable. It is also obviously a lot harder to get dry once you are wet in a cold environment.

As most people are aware the extremities are the hardest parts of the body to keep warm. Your feet and hands will almost always get cold especially if you are not moving them. Keep wiggling your toes and fingers in order to keep the blood circulating through your system.

Why fire is bad! .. sorta.. There is one reason why a fire can be harmful for keeping warm. If it goes out it can play a huge shock on the body (more for an emergency), but a person will be more comfortable when gradually heating / cooling. So don't sit 3 inches away from the fire, use it for a gentle warmth, not a burning

Fire Rocks and Water bottles veering away from the intense heat. These two items will slowly (water fairly quickly, but not as quick as fire) release their heat and make a person more constantly comfortable

Staying small will make you a more efficient heater, same with snuggling with another person. Armpits and Crotch (ewwww) are a good place to keep your hands warm. Just make sure they are clean ;) or you will not have many friends.

A lot of other points are already listed

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As others have said, your clothing, and lots of layers is important.

Additionally, the composition of your clothes matters.

Do not wear cotton in cold weather. "Cotton kills" is a common phrase amongst cold weather-goers.

Wear exclusively wool or wicking sythetic fabrics like fleece. Cotton's insulating ability goes to nearly zero when it is wet, and it absorbs moisture, so it keeps you wet.

Wool and synthetics retains their insulating ability even when soaking wet, and they also wicks water away, to keep you dry.

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Another point which hasn't been brought up yet is shelter. Have a look at these types of shelter which you can sometimes build:

  • Quinzhee
  • Igloo
  • Trench (Just dig a trench in the snow and cover it with a tarp. Also, dig another trench inside the sleeping trench to let the colder air sink there instead of where you sleep.)

You can also add insulation by planting fir boughs in the ground at an angle. This gives the boughs a little spring and they form a layer of air under you, similar to having another matress.

Oh, also, a candle can help heat your shelter to a certain extent, but it also helps in drying the air, especially in a tent, quinzhee or igloo.

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I've not camped in subzero weather before but I have spent several hours working on glaciers. The things I've found really helpful have been lots of layers. Typically I would wear the following. Thermal underwear, tshirt, jumper, fleece, ski-jacket, rain-coat & trousers, sallopettes and waterproof trousers. Along with thick socks and decent boots, hat, neck warmer and gloves. I found having several pairs of gloves handy as when wet they lose their warmth.

As for sleeping I've probably camped out in sub zero - I've just never had a thermometer with me to check. I've found a good mummy bag (wrapped in a blanket if it's really cold) on an airbed enough.

Other tips to bear in mind are the ground is cold is insulate underneath yourself as well as on top. One trick is to use an airbed on top of a roll matt. The smaller the tent the better as it will trap some warmth in, an obviously a smaller tent will warm up from your breath quicker than a big tent. Lagerbaer also makes very good points which I was beaten to making. :) Also things like cup-a-soups are good for warming you up.

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  1. More insulation.
  2. Stay dry inside. Make sure you wear something that lets sweat escape.
  3. Keep your head covered with a hat and, if possible, a mask or balaclava.
  4. Eat plenty of food.
  5. When you stop, you will probably want to be doing something, stand at a fire, or get in your sleeping bag. It's hard to just stand around in sub-zero weather without getting cold.
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If you're staying out overnight, consider digging a snowhole instead of using a tent. A snowhole can be much warmer than a tent and give significantly better protection. And, as Andy Kirkpatrick writes, they can't blow away.

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I have slept in freezing temps and sub zero. All I will say is most sleeping bags will not even keep you comfortable to half their rating. Get a good bag, add a thick blanket or two, and wear plenty of layers.

Do not forget a head and face covering. A few days ago I slept outdoors in -12F and I used a triple layer extreme cold military bag inside a commercial bag rated to -25F and I was mostly comfortable.

Anything extra you can do is recommended. Like building a debris shelter, digging a trench to block wind etc.

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Put layers on your ground sheet: cardboard (keep it dry), bubble wrap, survival bags, or blankets will do. These will mean the tent does not lose heat to the ground.

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Also, I'd like to add stay out of the wind. The wind will suck away any heat you build up, and unless you have a strong tent, cold air will pour in through the seams. One time we were dumb enough to camp on a mountain bald with no trees to protect us in a steady 40 mph wind and a member of our group was in early stages of hypothermia before we were able to get off the mountain top.

Another tip, you're only as warm as your coldest group member so if there's someone who is freezing, focus on heating them up and make sure they're giving you accurate responses to their condition. People experiencing hypothermia usually first start acting irrationally.

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There are two components to staying warm and it's all generally centred around thermodynamics. You want to stay at one temperature and physics wants you to become the temperature of the your environment.

You body, if 100% efficiently insulated, would get hotter and hotter because it's generating heat from all the bodily processes and chemical reactions going on, especailly movement. The source of this heat energy is food which is processed and/or stored in your body and if no fuel is going in, then your body itself.

Equally, if you were 0% insulated, you would cool down at a rate proportionate to the difference in temperature between you and the outside world. To this, you add the heat energy you're generating and ultimately you get a rate of decrease in temperature.

Somewhere between the two is a level of insulation which essentially allows you to create an equilibrium between the rate of generation of heat and the rate of loss. This is how you stay the right temperature.

So some tips are:

  • Wrap up warmer as soon as activity stops. You're about to generate less heat, so balance.
  • Keep out of the wind: wind increases heat loss.
  • Keep dry: water is a good conductor of heat, away from you.
  • Don't sweat. If you are getting hot, ventilate your clothes to increase your heat loss so you don't sweat and get wet (see above)
  • Keep well fed, you need fuel to keep generating that heat internally.
  • Eat before bed. Digestion creates heat, and you'll want that heat in the middle of the night.
  • Don't get your sleeping bag dirty. The dirt will fill in the lovely air gaps which are the best insulators. And don't sweat in it (see above)
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