How not to freeze in a tent: advice from experienced tourists
When it's cold, no hike is enjoyable. It often happens that you go hiking in the summer, climb into the mountains, and find frost. Or you expect a golden autumn but get a week of snowfall. During the day, it’s not so bad: while walking under a backpack, it’s warm, and under the sun, it’s hot even in frost. At night in the tent, you can’t sleep from the cold, you shiver, curl up into a ball, and count the minutes until dawn, and in the morning, you have no desire to go further. To avoid this, you need to prepare both technically and mentally, meaning you should choose gear suitable for the conditions of the hike and know what to do if something goes wrong. There are proven techniques for how to prepare for the cold in advance and what to do if you went on a summer hike and ended up in the snow.
What to do before the hike
Find out as much as possible about the conditions of the hike: at what altitude you will be sleeping, what temperatures are expected at night, whether there will be snow, and what surprises the weather might bring this season. If you are going on a hike in winter or in the off-season, prepare for the cold and choose the right gear. The right gear means suitable for specific conditions. Once you have gathered all the information, you can start selecting the right equipment.
Choose the right sleeping bag and mat
The first and foremost rule to help you not freeze at night is to take a sleeping bag that matches the conditions of the hike. The main thing to look for when choosing a sleeping bag is the comfort temperature. Not the extreme temperature, but the comfort one. Find out the approximate temperatures expected at night in the area of your trip and choose a corresponding sleeping bag. If you are going into the mountains in the off-season when it can suddenly get cold without warning, take a sleeping bag with a “reserve” of 5-7 degrees. For example, if you are hiking in the fall and the expected night temperatures are around zero, but snow may suddenly fall—take a sleeping bag rated for minus five.
Frost-resistant individuals can rely on the lower comfort temperature, while those who feel the cold can only rely on the upper temperature.
For mats, the comfort temperature is indicated by the R-Value rating; the higher it is, the better. A thin Izhevsk mat is not suitable for sub-zero temperatures; it freezes quickly. A thick three-layer Izhevsk foam mat is suitable for sleeping on snow. For winter and off-season hikes, it’s advisable to take thick foam mats or 4-season self-inflating mats: they provide good thermal insulation and comfort.
Never choose a sleeping bag based on the extreme temperature. That’s the temperature at which you won’t die. But you probably won’t sleep either.
Use a warm liner
If for some reason you can’t take a warm sleeping bag, take what you have plus a liner for the sleeping bag. They can be thin, made of cotton or silk, and warm, made of fleece or other synthetic insulation like Thermolite.
The thin ones are used solely for hygiene purposes—to avoid dirtying the sleeping bag with dirty socks, for example. However, warm liners significantly increase the comfort temperature due to the material itself and the additional air layer between the liner and the sleeping bag.
Make a double sleeping bag
A double sleeping bag is two sleeping bags zipped together. Ideally, they should be the same model with left and right zippers, although sometimes it’s possible to zip together even sleeping bags from different brands—just make sure to check before the hike if it can be done. A couple who always plans to go on winter hikes together can buy a double sleeping bag and solve the cold problem forever, saving on weight as well.
Stock up on a heater
There are different types of heaters.
The most universal is a catalytic heater—an indispensable item for winter and generally cold hikes. It’s a compact heater that warms hands, feet, or any other part of the body, dries shoes or gloves, and most importantly, raises the temperature in the sleeping bag for the entire night. The heater runs on gasoline and is completely safe because there is no open flame, and a special protective thermal cover prevents burns.
It works simply: fill the heater with fuel, light the wick, close it, and place it in the sleeping bag. It can heat for several hours to a day, depending on the model and amount of fuel. You can fill it with the popular tourist gasoline "Kalosha" or refined lighter fluid. The most popular heaters are made by Kovea and Zippo. They can be purchased in stores for tourists or fishermen.
Salt self-heating pads are designed to warm hands and feet: at night, they can be placed in gloves or socks to keep warm. These pads can be single-use or reusable.
If you don’t have a catalytic heater, you can improvise one using a plastic bottle or flask. Heat water, pour it into the container, and place it in the sleeping bag. If you’re not conserving gas, you can make two such heaters: one for your feet and the other to cuddle with while sleeping. Flasks can always be borrowed from those who don’t freeze. Such a heater gives off heat for several hours, and then it’s better to take it out—sleeping with cold water isn’t very pleasant.
Important
Do not pour boiling hot water into a plastic bottle, or you’ll have to throw it away later. Just don’t bring the water to a boil or cool it a bit if you didn’t keep an eye on it.
A catalytic heater will help raise the temperature in the sleeping bag.
What to do during the hike
If you suddenly encounter bad weather or it gets cold sharply during the hike, and you have unsuitable equipment, just a summer sleeping bag and a thin mat, the main thing is not to panic. You’ll have to improvise and warm up with what you have. We’ve already talked about the bottle heater, but there are other ways to keep warm.
Insulate the sleeping bag from the cold ground
If frost hits suddenly, and you only have a thin foam mat, place everything you’re not wearing under the mat.
Your task is to insulate yourself from the ground as much as possible. Ask your companions for seat pads and place them under your lower back—this is where your back gets cold the most. Empty everything from your backpack, fold unnecessary clothing under your back, and put the backpack under your feet. It may not create a very even surface, but it will definitely be warmer.
If you have a rope—that’s even better; climbers sleep on it without any mats, so you can manage too.
It may be uncomfortable, but it will be warm. As a last resort, place a folded emergency blanket under your back—it’s not as effective as a normal warm mat, but better than nothing.
Go to sleep in clothes
Some believe that sleeping without clothes in a sleeping bag is warmer. This is a debatable question, and in reality, it all depends on the comfort temperature of the sleeping bag and the temperature outside. Try to bring a spare set of clothes for sleeping. Ideally, this should be warm thermal underwear, such as merino wool or Polartec Power Stretch. Never sleep in wet clothes; this is the best way to freeze. There are many debates about whether it’s warmer to sleep in a sleeping bag with clothes on or without. Some claim that the sleeping bag doesn’t warm as well when dressed, but there’s only a small grain of truth in that. You shouldn’t put on all your clothes and crawl into the sleeping bag in them—you won’t warm up that way. But sleeping in thermal underwear is definitely warmer than without it. If it’s cold to sleep in just thermal underwear—layer up. Bulky items like a down jacket are better not to wear but to throw over the top. If you toss and turn a lot in your sleep, place the jacket inside the sleeping bag; otherwise, it will slip down, and you’ll have to unzip the sleeping bag to adjust it. And wear wool socks or down booties, a fleece, pants, and a hat. Warm up the parts that get coldest; for example, you can tuck your feet into a zipped fleece jacket.
When it’s cold, it’s okay and necessary to sleep dressed in a sleeping bag. But it’s better not to put on all your clothes; for example, it’s better to throw a down jacket over the top.
Warm your head and feet
People often forget about the head, which is a mistake: a lot of heat escapes through the head. Wearing a warm hat and tightening the sleeping bag’s hood will make it noticeably warmer. For those who feel the cold especially: if you have a lot of warm clothing, don’t wear it all at once; instead, warm your head and neck, for example, by wrapping them in fleece or a down jacket. This way, you’ll also prevent heat loss from the sleeping bag. You must wear socks on your feet, but not the same ones you wore on the trail; instead, wear looser and warmer ones so your feet are comfortable and nothing is pinching. The best socks for sleeping are made of Polartec or soft wool.
Eat before sleeping
A hike is not the time for diets. The colder the hike, the more you need to eat. There’s no time for diets—food should be calorie-dense, and it must be hot before bed. Food is energy, and energy is heat, so the more energy in the form of dinner your body receives before sleeping, the warmer you will be at night.
Calories are directly related to heat, not excess weight. For a cold hike, it’s better to take high-calorie food rich in fats and carbohydrates. For example, peanut butter, chocolate, nuts, pemmican… In the cold, some foods can freeze so hard that you can’t bite into them (for example, chocolate bars with peanuts), so plan your food carefully. Ghee is very convenient in winter: it doesn’t spill and doesn’t melt. Hot soup with pemmican and ghee is a great example of a proper dinner for a cold evening.
Eat hot food as often as possible because cold food requires energy from the body to warm it up. It should be the other way around: food warms you, not you warming the food.
Warm up before getting into the sleeping bag
Don’t go to sleep frozen—otherwise, you won’t warm up soon (or at all). A sleeping bag doesn’t warm you; it only retains the heat your body generates. If your body is cold, it has nothing to give off, and the sleeping bag won’t help much. So before you get into the sleeping bag, try to warm up in any way possible.
It’s good if there’s a campfire; you can warm up by it. If not, do some physical exercises: you can step out of the tent and do 50 squats, jump around, or chop wood. It’s important to warm up but not to sweat. You can drink hot tea before bed (even in the sleeping bag, just be careful not to spill), but don’t overdo it with the amount so you won’t have to go out into the cold in the middle of the night.
Try not to leave the tent
Every time you go outside, you cool down both yourself and the tent, especially if the entrance is facing the wind. If you step out, all your efforts to heat up will be wasted. So try not to leave the tent without a good reason. Before bed, drink less tea, and if you still need to go, use a sealed container for this purpose—like a plastic bottle with a wide mouth. There are also special devices for women, which can be handy. There’s no time for ceremony here.
And if you do have to go out, remember the point about warming up and do at least ten squats to get back into the sleeping bag warmed up.
Warm each other with body heat
There’s an old saying: “One Indian under a blanket freezes, two Indians under a blanket don’t freeze.” If it’s cold at night, there’s no time for shyness—snuggle up to each other tightly to keep warm. Nothing warms better than the body heat of another person. If that doesn’t help, try zipping two sleeping bags together. Usually, a double sleeping bag is made from identical models with right and left zippers, but sometimes it’s possible to zip together different sleeping bags (but they still need to be right and left).
Warm up the tent with a stove
All manufacturers of tents and stoves strictly prohibit this, but tourists still do it to warm up. We also do not recommend it, but since you probably won’t listen anyway, we will tell you how to do it as safely as possible.
This method should be used very cautiously and only as a last resort if you are very cold and cannot warm up any other way. You can briefly turn on the stove in the tent; it will raise the temperature inside and help you warm up and fall asleep. It’s important to remember that this is unsafe: first, you can get poisoned by combustion products, and second, a tent can catch fire in 30 seconds. So if you decide to do this, follow these rules:
Open all ventilation windows: in an unventilated tent, it’s easy to suffocate (or drown in condensation).
Never sleep with the stove on. It’s better to turn on a strong flame for a few minutes to quickly warm the tent and then turn off the stove than to leave a weak flame on and accidentally fall asleep. This is not a heater; you need to watch the flame carefully.
For heating the tent, use only tested gas canisters that have already been partially used.
Low-quality canisters often explode at the wrong moment.
Among gas stoves, the MSR Reactor looks the most appealing for heating—it has no open flame, the flame is covered by a “cap” made of porous ceramic, and the gas consumption is minimal. However, these stoves generate more carbon monoxide than others, which can be deadly. In reality, it turned out to be not so scary: experienced mountain tourists conducted a study measuring the carbon monoxide levels in a tent with a working “reactor.”
The conclusion was that the stove generates almost no CO without a pot, meaning you can safely warm up and dry off. The main thing is not to forget to ventilate the tent. However, this lets heat escape, so there’s not much point in this method.
So, the best way not to freeze at night in a tent is to choose the right equipment. The sleeping bag and mat should match the conditions of the hike, so you won’t have to deal with bottles or mess around with the stove. But if the frost hits suddenly and you have a summer sleeping bag—you know what to do.