Guide 3 min
A 0 C sleeping bag, what season is it for?
A 0 C comfort bag covers spring and autumn in the lowlands. At 1500 m your night drops to -9 C, so it no longer holds. And in summer it's too warm.
A sleeping bag rated 0 °C comfort is a spring and autumn bag for the lowlands. Both seasons drop to 0 °C at night, and the rule fits on one line: the bag's comfort temperature has to stay below the night you expect. At 0 °C comfort for a 0 °C night, it lands exactly right.
The catch is that "0 °C" tells you nothing about your terrain. The same label turns too tight the moment you gain altitude, and too warm in high summer. Here are the three cases where a 0 °C bag changes its role, and the sum that separates them.
The rule is simple: comfort drops below the night
WildKit doesn't read the season off the label, it reads the night. A bag works if its comfort temperature is less than or equal to the night you expect. Below that night, you're cold. Too far above it, and you're carrying down for nothing: past 8 °C of gap between the bag's comfort and the night, the bag is set aside, too warm and too heavy for the trip.
By season, in the lowlands, a 0 C bag doesn't always play the same role
At zero altitude, each season has its typical night. Here's what a 0 °C comfort bag gives you against it:
| Season | Night in the lowlands | A 0 °C comfort bag |
|---|---|---|
| Spring | 0 °C | lands exactly right |
| Summer | 10 °C | too warm (10 °C gap) |
| Autumn | 0 °C | lands exactly right |
| Winter | -5 °C | too cold |
Only two seasons out of four really suit it. Spring and autumn fall exactly on its comfort point. Summer and winter push it out of its zone, each in the opposite direction.
Altitude changes everything: count -6 C per 1000 m
Your night doesn't depend on the calendar alone. It drops by 6 °C for every 1000 metres. The sum: night = the season's temperature minus 6 times the altitude in kilometres. So a spring night at 1500 m isn't 0 °C but -9 °C (0 minus 6 times 1.5). Your 0 °C comfort bag no longer covers it: you're 9 °C short.
This is the classic trap. You set off "in spring", you climb up to the refuge, and the bag sold for the season leaves you shivering. At that altitude, think about the ground too: a good bag is useless if the cold seeps up from below (see the sleeping bag and mat pairing for a cold night).
In summer, a 0 C bag is too warm, not too cold
Summer in the lowlands drops to 10 °C at night. A 0 °C comfort bag covers that easily, and that's exactly the problem: 10 °C of gap between the bag's comfort and the night. Past 8 °C, WildKit sets it aside. You sweat, and you're lugging a bag heavier and bulkier than you need. In summer, aim for a bag whose comfort sits close to 10 °C, not a model cut for the shoulder seasons.
What to remember
- A 0 °C comfort bag covers spring and autumn in the lowlands (0 °C night): it falls exactly on its comfort point.
- Add -6 °C per 1000 m: at 1500 m your night drops to -9 °C, and the 0 °C bag is no longer enough.
- In summer (10 °C night), the gap reaches 10 °C: too warm, WildKit sets it aside past 8 °C.
You choose a sleeping bag on the real night, not on the season printed on it: that's what decides whether you sleep well or shiver. Give us your trip (season and altitude), and watch the calculated night appear alongside the sleeping bag that actually holds it.
A guide WildKit keeps up to date. Published .