Warmth ratings are a guide, not a rule. The degree listed on a sleeping bag is a measure of a bag’s comfort zone. Typically, a 20-degree bag will keep the average user comfortable at 20 degrees, but we all regulate heat differently.
Many bags, like the Kelty Cosmic 20, feature dual zippers. This allows the bottom of the zipper to be opened as a vent while most of the bag stays zipped shut.
If you run cold, a 20-degree bag may feel too cold in 30-degree temps. If you run hot, you can get away with a 30-degree bag in 15-degree weather or below. Keep this in mind if you run hot or cold on either end of the spectrum.
A good night’s rest starts with a solid sleeping bag; (photo/Eric Phillips)