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Related Questions: Keeping warm in an emergency, Light-weight emergency overnight-gear

It has happened to me a couple of times that I have shelter and plenty of insulation underneath, but my 1-season sleeping bag turns out insufficient for the spring snow that surprised me at nightfall. What should be done in such conditions?

I have tried:

  • Enabling alarm every 30min or one hour in order to prevent white death
  • Zipping the bag all the way, only my nose protruding. Unfortunately below freezing temperature breathing the icy air is very very uncomfortable.
  • Zipping the sleeping bag and forming a ball inside. Unfortunately everything turns wet by the morning and even before that.
  • Emptying my backpack and wearing it as one large sock over the sleeping bag. This really helps!

Heck, how do people in quality sleeping bags sleep in the winter with all that sub-zero air that they have to breath?

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    Are you actually able to fall asleep when you're freezing cold? – gerrit Jul 5 '13 at 9:35
  • @gerrit, intermittently yes. Rolling around warms a little and being scared tires down. – Vorac Jul 5 '13 at 9:41
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    I've slept in -20C with no problem in a good down sleeping bag. If your body's is snug and warm, it can easily handle the influx of cold air. – Lagerbaer Jul 5 '13 at 14:45
  • Why does everything turns wet? I believe that is one important factor that you should try to prevent from happening. – ppl Jul 6 '13 at 1:10
  • BTW - you might think about what else is in your pack - sometimes you just need a little extra help, like a poncho thrown over your bag. – Don Branson Jul 6 '13 at 1:39
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It is worth nothing that if you have a cooking system and the extra fuel you can prepare hot water and place the hot water bottle between your legs to help you keep warm.

If you have extra food, eat a high-energy snack before going to bed.

Other things that comes to mind are: cover your head, use what you can as bottom insulation, make sure you don't overheat and sweat.

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  • Hot water bottle - what a great idea - wish I'd thought of this on a couple occasions. – Don Branson Jul 6 '13 at 1:37
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    High-energy snack - that remind me that some people will have a spoonful of peanut butter before settling for the night to help stay warm. – Don Branson Jul 6 '13 at 1:38
  • By the way, a large soda bottle stuffed into a wool sock makes for an excellent improvised hot water bottle. Just don't let the water get too hot (about 50 °C / 120 °F, or barely touchable, is still OK) or the plastic may degrade. – Ilmari Karonen Jul 20 '13 at 20:46
  • +1 for cover your head. Even if in the sleeping back, put on a cap, hood or anything else. Its crazy how much heat you loose through your head (can be 40%+). – Paul Paulsen Apr 28 '14 at 22:43
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I've only once experienced a nights' sleep that my sleeping bag didn't handle. I was only 200 metre from civilisation, and I hardly slept, but it was not really dangerous. I'd expected temperatures around 0°C, but it turned out to be the local coldest night of the year at -7°C.

Å i Lofoten, 27 March 2008
Normally, the gulf stream means that at Å i Lofoten, Norway, temperatures usually don't drop far below 0°C, but on the early morning of 27 March 2008, it was the coldest night of the year at -7°C.

If you're worried that falling asleep may be lethal, I would simply not even try to sleep. Get out of your tent, eat, pick up your tent and walk away. Hopefully you brought some decent headlight, but even if not, as long as you're walking, even just back and forth or in circles around your tent, you can keep warm and you won't fall asleep. You'll get very tired, but being tired is not lethal, and perhaps during the day it gets warm enough to sleep safely.

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People falling asleep and dying were already affected by hypothermia, once it happens to you, the only chance is a heat source such as fire or other people, however if you are alone, you will have really problems with making fire in such condition.

If your body isn't completely exhausted, you will have great problems falling asleep, if you will be freezing. This is a measure how a comfort and tolerance temperature ranges for sleeping bags are measured: comfort range means you'll be able to sleep the whole night, while tolerance range means you'll wake up a few times an hour because of freezing.

In extreme cases just sleep in your clothes , treating sleeping bag as just another warming layer. You can also put your legs (being in sleeping bag) into your rucksack - it will provide another isolating layer.

And finally, if the night isn't too dark, consider walking in night and sleeping a bit in the day, when it's a bit warmer.

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You ought to bring an emergency blanket with you, they’re tiny and very lightweight and will increase your temperature significantly. You do get wet with them though, and they are an emergency solution. For me it was a lifesaver when I was unprepared in the Simien mountains where it freezes as night and the other gear was absolutely not sufficient.

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You say you had sufficient insulation underneath, but more will always help. I used to spread my towels under my foam sleeping mat when winter car-camping for kayaking (sub-zero overnight). It didn't matter that they were damp, under a closed-cell mat (though that discouraged me from using them as blankets), and they certainly added to the insulation. Admittedly I was lucky to have 2 full-size towels with me (one for river/sea water and one for after a shower).

It's important to keep draughts away - so consider your tent's ventilation. Normally I have a little at the top and bottom, but if it's really cold I close the bottom ventilation. If you're under a tarp, you'll need a good windbreak.

On top of you, as you found, kitbags of any kind are good for tucking your feet in. For your upper half, you can drape an (ideally breathable) waterproof jacket over the outside of your bag, and tie the sleeves together underneath at shoulder height. The insulation value is low, but it's extra draught-proofing. A fleece can be used similarly, though I preferred to use mine to form a hooded micro-climate around my head, aided by whatever I had to hand, perhaps fastening the sleeves to hanging lops in my tent.

A hat of course helps, as does plenty of clothing around your shoulders and neck. I'm at the maximum height for my sleeping bag and move a lot in my sleep, so tend to open up draughts around the sleeping bag hood - any hooded top would be good.

If you can prepare even a little in advance, any liner adds a useful bit of warmth. Mine is polycotton, like a bedsheet, and indeed you could improvise one at home from a sheet with safety pins. I almost always have a liner with me, as it's good in warmer weather too (combined with unzipping the sleeping bag) and good for keeping the sleeping bag clean. If I had to make my sleeping bag warmer at a few hours' notice, I'd grab a fleece blanket and the sewing machine to make a warm liner.

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Bit late to the party, but here goes:

 my 1-season sleeping bag turns out insufficient for the spring snow that surprised me at nightfall.

Well, that one season the sleeping bag refers to is not spring...

What should be done in such conditions?

  • In any case: Eat, preferrably hot food: you need your body to have sufficient fuel to produce heat to keep you warm. Sugar (sweets) before you start cooking give you energy that is avalable almost instantaneously, until the longer lasting nutrients from a full meal kick in. I've also found protein-rich stuff to really help in miserable conditions (e.g. a mug of thick, sweet cocoa with extra milk powder or protein powder can to miracles).
    Exhaustion including being hungry are major contributing factors to hypothermia (and while we're at it, the conditions that got you exhausted & hungry often also favor dehydration).

  • What should have been done before: the day's tour should have been kept sufficiently easy/short so you are not exhausted. I.e. you have physical and mental reserves to take action during the night as required, once you're "refueled".

  • Break camp and hike out/to the next hut or at least in that direction.
    Unless the conditions do not allow safe hiking out (e.g. ongoing snow storm, whiteout, you being night-blind) this is often the safest action you can take when you really do not have sufficient equipment for the conditions you find yourself in. Even in not light-polluted areas snow on the ground gives me sufficient light to hike. You want to hike slowly, so as to avoid exhaustion and accidents. Put on sufficient clothing to keep warm at a slow speed.

If you decide the situation is not that bad, so you can stay in camp:

  • Close your shelter as well as possible. With a tarp, go for a low setup with steep roof (because of snow), e.g. a bivy or forrester setup or a variation of the body bag with closed foot end or both ends closed.
    The smaller the tarp space is, the warmer you'll be. If you close the head end, you'll have moisture, though (from breathing).

    If "good insulation below" refers to twigs & leaves, you can add branches and leaves onto your tarp. (I assume surprise spring snow to be wet and thus not very suitable for insulation)

  • Put on all your dry clothes. I'd leave moist raingear outside as additional blanket.

  • If the sleeping bag is too small & tight for that, put them outside as blankets

  • After eating and before crawling into your sleeping bag, make sure your're warm - including toes, finger tips, ears and nose. If necessary, some excercise can help.

  • When waking up cold:

    • if you need to go to the loo or are hungry or thirsty, take care of that, then do excercises until warm again.
    • If there is no other need to leave your sleeping bag, static excercises are good for generating heat as well. Know a variety that warms you up.
  • There is no whatsoever point in waiting to get warm in the circumstances you describe, so take appropriate action.
    Keep in mind that you need to act appropriately with mild hypothermia: it is the last (only) stage of hypothermia where you can rely on your brain functioning sufficiently well to take good decisions.

  • The backpack can help in two positions:

    • as you describe as additional blanket/toe box, or
    • to close your shelter.
  • If your sleeping bag is sufficiently large to let your curl up, do that - I'd keep my nose outside because of the moisture problem you describe.

  • When you curl up in your sleeping bag, the lower part is unoccupied. Turn that either below for additional insulation from the ground or up as additional blanket, whereever it helps most.

  • If you really have to spend the night completely inside the sleeping bag, as you describe it will get moist, and this impairs the insulation. This means that you must hike out the next day.

  • Space blankets have been mentioned. A bivy sack comes in the same category.

Enabling alarm every 30min or one hour in order to prevent white death

That is not necessary or even counterproductive since it may disturb the little sleep you are able to get whenever you are sufficiently warm.

If you are generally healthy, well fed and not under the influence of drugs (meaning not only alcohol/recreational drugs but also medication), there is no danger of getting into hypothermia and dying during your sleep. You'll wake up reliably when getting cold.

BTW, even quite exhausted muscles will produce substantial amounts of heat when they repair themselves during rest. The repair processes need protein and general excess energy (= well fed, otherwise the protein will be used as energy source).

What is sometimes popularly described as "falling asleep and freezing to death" is IMHO a misconception. People with severe hypothermia do not fall into anything like normal sleep, they fall into stupor, become unconscious and comatose. AFAIK, also terminal burrowing (aka hide-and-die) is not a conscious action like trying to get warm and cosy in order to sleep.


 how do people in quality sleeping bags sleep in the winter with all that sub-zero air that they have to breath?

Speaking for myself, cold acclimatization does play a major role: my nose (ears and fingers) take a few cold days to remember that they need to heat more when it gets cold. If you always spend substantial time outdoors, your nose will be used to work with those temperatures. Apparently, exposing face, neck and breast to cold air stimulates thyroid cold acclimatization (that's more general, though, we're talking weeks, not a single night).
I've slept in dry -2X °C on top of my tarp (so not to get soaked by snow I accidentally melt) without problems breathing the air in February in Winnipeg - those -2X °C were after all much warmer than the -35 - -40 °C in January... I did use a scarf, creamed my cheeks and nose well with vaseline/petroleum jelly and used the sleeping bag's hood. (Covering my nose makes me miserable because of the freezing moisture). That occasion was a test of my sleeping bag I did in the garden before I went for a proper tour, btw.

The human nose has no general problem with staying warm in calm cold air - as long as sufficient energy is available to generate the required heat.

At temperatures substantially below 0 °C, the air is always very dry unless there is fog. This helps a lot with staying dry which is in turn important for staying warm. I find camping at +2 °C rain/sleet much more difficult than at -20°C.


A few more points to consider

  • A one-season sleeping bag can make a very nice (though bulky and heavy) "upgrade" to another sleeping bag if it is sufficiently large.

  • I typically bring gear that is good for about 10 °C colder than I expect (unless I'm only a few steps from house or car). I'll thus usually sleep with a large tarp e.g. in a C-setup, the tent door completely open and often also the sleeping bag used as a blanket with the zipper open. This gives a safety margin where I can put on more clothes, close the sleeping bag, close the tent or tarp. There's also nothing wrong with taking an extra blanket along (other than bulk/weight).

    I find it much easier to bring some more gear than to be miserable during the night.

  • While @gerrit is right that being tired but warm is better than being tired and cold (since you anyways won't sleep when cold), being tired is a safety concern as well.

  • Proper winter camping (on snow) has the advantage that a pulkka/toboggan mean that volume and weight of the gear is not very problematic.

  • The more extreme the conditions, the more safety margin should be kept. Not only in terms of gear, but also in terms of food and fuel and in terms of keeping sufficient personal reserve (physical and mental).

  • Many sleeping bags IMHO are badly designed in a peculiar way: their back has much less insulation. The "reasoning" behind this is that this part is anyways compressed and won't isolate. However, that works only for those very orderly people who lie down like a mummy and stay in that position on their back without moving much for the whole night. If you sleep on your belly or on your side - including curling up egg-fashion because you're cold, you need good insulation at your back.
    My warmest sleeping bag has this issue, and in consequence I've been known to sleeping quite twisted: my back in the sleeping bag's belly side, the cap turned around as far as it goes or folded as head rest and scarf + woolen cap instead of the sleeping bag's cap.

  • Test your personal comfort temperature range for your sleeping bag by spending calm dry nights outdoors close to your home (with at most a tarp put as a roof to keep rain/dew away). Forget the manufactuer's claims until you know how to translate them to your camping habits.

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