I am looking to buy an ultralight sleeping bag, that would be warm enough for sleeping in the Alps in summer comfortably. I would be sleeping in a tent on a sleeping mat. I would probably be staying at around 2000, max 2500 meters. And I would expect I could be out there in between June and September. According to my research on the Internet, the lowest temperatures at that time and altitude should be around 0°C, possibly a couple degrees below, but most likelly a bit above. How warm do I need the sleeping bag to be?
Actually, I believe my question can be subdivided in the following subquestions:
- Can I safelly assume, that it will not get much below 0°C in summer in the Alps at around 2000 meters altitude?
- How much warmer will it be inside a tent? (very small two-person tent, two layers, no heaters)
- Sleeping bags have temperature ratings for three categories: comfort, limit and extreem. Should I look at the lowest value of "comfort" temperature if I want to be able to sleep without feeling cold?
So I have bought a sleeping bag, and would like to update the question with my experience.
I have decided to go with the ultralight (and expensive) option in the end. My new sleeping bag is rated +4°C comfort, and -1°C limit. I have tested it on a few trips in the mountains during this summer. When sleeping on warm summer nights at altitudes around 1500m, it was actually too warm. No surprise there, and not a problem either.
Another trip I took was in the end of September, when the nights were fairly cold already. I am not sure about the exact temperature, but it must have been in between 0 and 5°C. I was sleeping at around 2400. I must admit, I was a bit worried, but the only time I was cold was while cooking dinner outside of the tent. The sleeping bag combined with a cotton sleeping bag liner was certainly enough.