The comfort temperature is the one number that tells you how cold it can get and still have you sleeping soundly, and it's the figure to check before you buy or rent a sleeping bag. Labels carry three numbers (comfort, limit and extreme), and the most common mistake is reading the wrong one. If a bag says "-10", that's almost never the temperature you'll sleep comfortably at: it's usually the limit, or flat-out the survival rating. On our trips we check every traveler's bag beforehand, because a mistake here has no fix at three in the morning. In the video above we walk you through it in a minute, label in hand, with a real bag.
In short
Always look at the comfort rating, not the limit or the extreme.
Comfort: you sleep relaxed. Limit: you get through the night curled up. Extreme: survival, not rest.
Field rule: add 5°C of margin over the lowest temperature you expect that night.
The sleeping pad (its R-value) matters as much as the bag: without good insulation from the ground, no bag keeps you warm.
Down for weight and packability when it's dry; synthetic when there's damp or rain.
What do comfort, limit and extreme actually mean?
They're three temperatures measured under the EN/ISO standard, describing three different scenarios for the same bag. The comfort rating is the temperature at which a cold-prone person sleeps relaxed, stretched out, without waking up cold. The limit is the lowest temperature at which someone can sleep curled up without slipping toward hypothermia, uncomfortable but safe. The extreme is pure survival: you don't sleep, you don't rest, you just avoid dying. Nobody plans a night around the limit or the extreme.
The confusion comes from marketing pushing the lowest number: a "-15" sells better than "0°C comfort", even when they describe the same bag. That's why you should always go by the comfort figure.
To make it concrete: in the video we grab a bag whose label reads 16°C comfort. That 16 is the number you use to plan a mild night; if the same label carries a lower limit and extreme, those describe discomfort and survival, not rest. One practical tip when reading a label: always check the unit. Comfort usually comes in Celsius, and some brands add the Fahrenheit conversion next to it (16°C is about 61°F), so don't mix up one scale for the other when comparing bags.
| Rating | What it describes | How you sleep | When to use it as a reference |
|---|---|---|---|
| Comfort | Cold-prone person, stretched out | Relaxed, all night | Always. It's your planning number |
| Limit | Cold-tolerant person, curled up | You can sleep, but uncomfortable | Only as a safety cushion, never the target |
| Extreme | Risk of hypothermia | You don't sleep, you survive | Never plan for it. It's an alarm, not a usable spec |
How many degrees of margin should you add?
Add at least 5°C over the lowest temperature you expect that night, and pick the bag by the resulting comfort rating. If the forecast shows a low of 0°C, look for a bag with a comfort rating of -5°C or lower. That margin covers what the standard doesn't measure: wind, overnight damp, the fatigue built up after a long day, and the fact that almost nobody sleeps as "warm" as the standard test subject.
Some factors shift your real sleeping temperature more than you'd think. Eating something before bed, sleeping in dry, clean thermal layers, and not climbing into the bag in the sweaty clothes you hiked in all add real degrees. Wet clothing, on the other hand, steals heat all night. Never sleep in what you walked in if it ended up damp.
Does the sleeping pad matter as much as the bag?
Yes, and it's what almost everyone underestimates. The cold you feel at night comes mostly through the ground, because your body weight crushes the bag's fill against the floor and that flattened fill stops insulating. That's where the pad does its job, measured by its R-value: the higher it is, the more it insulates from the ground. An excellent bag on a poor pad will still leave your back freezing.
For cold mountain nights, go for a high R-value or combine two pads, a closed-cell foam one underneath and an inflatable on top. That combo adds insulation and protects you from a puncture. Before spending on a pricier bag, first check whether your pad is up to the night you're about to spend.
Down or synthetic for trekking in Argentina?
Down packs smaller and weighs less for the same warmth; synthetic keeps insulating even when wet and dries faster. On damp or rainy traverses, like Torres del Paine or the Tilcara-Calilegua traverse, synthetic or water-treated down gives you more peace of mind. For dry high-altitude terrain, where every gram counts in your pack, good-quality down performs better.
For Champaquí in summer, many people manage with a 0°C comfort bag plus a silk or polypropylene liner, which adds a few degrees and keeps the bag clean. In autumn and spring we raise the bar to -5°C comfort. For the Mendoza expeditions, like Vallecitos or Cerro El Plata, we ask for specs per departure: wind at altitude changes the whole calculation.
How does the choice change for a hut, a tent or a bivvy?
Where you sleep changes how many real degrees you need, so match the bag to it. In a shared hut, like on Champaquí or parts of the Paine W, other people's warmth and the walls add a few degrees; you can go with a slightly lighter bag. In a solo tent you lose that human warmth and the surrounding air cools more, so it's worth adding margin.
In a high-altitude bivvy, the demand is at its highest: we use expedition bags and prioritize the warmth-to-weight ratio over packability. Always carry a dry bag to store your sleeping bag, plus a liner: on long trips the sweat and moisture the fill absorbs cut its insulation, and a bag that started out perfect can fall short by day five. Air out the bag every morning you can.
How much does a good sleeping bag cost, and is renting worth it?
It depends on the temperature range and the fill, and for one-off trips renting often makes more sense. A three-season bag covers most of the Córdoba treks in season; an expedition bag is an investment that only pays off if you'll do high-altitude mountaineering regularly.
Reference prices for purchase and per-trip rental: [COMPLETAR MONS]. On the Mendoza expeditions we have gear to rent, so if you'll use an expedition bag just once, renting it almost always works out cheaper.
Frequently asked questions
Can I sleep comfortably at my bag's limit temperature?
No. At the limit temperature you'll be able to sleep curled up without risk of hypothermia, but uncomfortable and waking up cold. To really rest, always plan around the comfort temperature, not the limit.
What is a pad's R-value?
It's the measure of how much the pad insulates you from the cold ground. The higher the R-value, the more it protects you from the floor. It matters as much as the bag, because at night a good share of the cold comes from below, where the bag's fill gets crushed flat.
Does a liner add warmth?
Yes. A silk or polypropylene liner adds a few degrees of warmth and, above all, keeps the inside of the bag clean, which is key on long traverses where sweat cuts the fill's insulation over the days.
Down or synthetic for rain?
Synthetic, or water-treated down. Synthetic keeps insulating when wet and dries faster, ideal for damp areas like Torres del Paine. Regular down loses almost all its warming power once soaked, so in the rain it's riskier.
How do I know my bag is enough for the trip I picked?
Check the expected low for those dates and that altitude, add 5°C of margin, and compare it with your bag's comfort rating. If it doesn't add up, message us: we'll read the label with you and tell you whether it's enough or renting is the way to go.
Sort out the doubt before you head out
Before your next trip, send us a photo of your bag's label on WhatsApp at +54 9 3512 11-3842. We'll tell you if it's enough for the date you chose or if renting in Mendoza is the smarter move. If you're still putting together the rest of your kit, our definitive guide to choosing your mountain clothing can help, and you can check the available dates on the departures calendar or the full list of activities.