There are many factors that determine how warm you will feel in a sleeping bag. Some of these factors include:
- What you wear. EN 13537 test ratings are based on the user wearing one layer of long underwear and a hat, but if you know you sleep cold, layer up!
- The sleeping pad you use. Your pad should have a minimum comfort range similar to your bag.
- What you eat before bed. Having a full belly of fuel will allow your internal furnace to keep you warm until morning.
- Where you pitch your tent. Sleeping on a tent platform, large rocks, or other thermally ineffective insulators can cause you to lose heat much quicker than sleeping on dirt or grass.