Only comfort and limit values play a role in your purchasing decision. If you tend to get cold, always rely on the comfort value. If you are less sensitive to cold, look towards the limit value. The extreme value is only relevant for expeditions and Alpine excursions, where the sleeping bag literally determines survival until the arrival of an emergency rescue team. Otherwise it doesn’t mean much.
The comfort temperature is usually reached with the hood and draft collar closed. Sleeping bags with a comfort range up to about 10 °C are called summer sleeping bags, those with a comfort range up to around 10 °C three-season sleeping bags and thick bags with comfort temperatures well into the negative degree range are noted as winter sleeping bags.
Our Tip for Determining the Right Temperature Value:
Be realistic about how you use your sleeping bag and don't buy one that’s too thick and warm out of a false sense of security. This costs not only money, pack size and weight, but also comfort since it can cause excess perspiration. It is best to buy one that suits your needs and allow for a little bit of leeway. If it does get a little colder, there are ways to "tune" sleeping bags a bit more. We elaborate more on this under the following section: