Most TETON Sports sleeping bags are survival rated (our ALTOS Down and LEEF sleeping bags are EN rated). This means that a bag rated for -10°F will keep you alive at a temperature down to -10°F. That doesn’t mean you’ll be comfortable.
To Get a Comfort Rating
For comfort, most people need a sleeping bag rated about 20°F to 25°F colder than the expected nighttime temperature on their camping trip. If you are expecting 0°F nights, then buy a -20°F to -25°F sleeping bag.
For information regarding EN ratings check out What is an EN rated sleeping bag and which TETON Sports sleeping bags are EN rated?