I get a lot of questions from SectionHiker readers asking whether their sleeping bags will be warm enough for their backpacking and camping trips.
“I’m starting an Appalachian Trail thru-hike in February at Springer Mountain. Will a 20 degree bag be warm enough?”
“My son has to go winter camping with his Boy Scout Troop. We live in Rhode Island. Will his 20 degree bag be warm enough?
It’s not that they don’t trust the temperature ratings of their sleeping bags, which have become quite reliable since US manufacturers adopted temperature rating standards (at the insistence of REI).
The question they’re really asking is what the temperature outside will be on the given date and location for their trip. The answer is to look up historical temperature averages.
Historical Temperature Averages
You can figure out the expected season temperature for any US location using historical weather information published at Weather Underground (Wunderground.com). I use this tool for planning most of my trips. Go to the Weather Underground website and click on the MORE menu item to access Historical Weather.
For example, you’d type in the name of the closest town to where you plan to start your trip and the date you plan to start. I usually pick that week rather than a specific day and average the temperatures from the past 3-5 years to get a reliable estimated max, mean, and average temperature. I can then mix and match the sleeping insulation I bring on my trip based on these numbers.
Depending on the season, I like to add about 10 degrees of extra warmth to my sleep system in case there’s a cold snap. For example, if the average is 30 degrees, I’ll bring a 20 degree sleeping bag or the equivalent quilt-based system.
Sleeping Bag Temperature Ratings
Sleeping bags temperature ratings assume you will be using an insulating sleeping pad, wearing long underwear, and a warm hat at night. That’s just how the standards work. So don’t skimp on these components of your sleep system.
If you’re a cold sleeper, here are some additional posts about other techniques and information you can use to sleep warmer at night on backpacking and camping trips.