Fall Camping: How to Stay Warm When Nights Drop Below 40

Fall might be the best camping season of the year. The bugs are gone, the campgrounds are quieter, the leaves are turning, and a campfire finally feels like it's earning its keep. The one thing that ruins a fall trip is a miserable night shivering in the tent at 3 a.m.

The good news: staying warm when it drops into the 30s isn't about expensive gear. It's mostly about understanding how you lose heat and plugging the leaks.

01Know what your sleeping bag rating actually means

That number on the bag isn't a promise. Most quality bags are now tested under the ISO 23537 standard (it replaced the older EN 13537). In a lab, a heated mannequin lies inside the bag in a climate-controlled room, and the bag gets two key numbers:

• Comfort rating: the lowest temperature at which an average person can sleep comfortably lying relaxed on their back. If you sleep cold, buy to this number.
• Limit (lower limit) rating: the lowest temperature at which an average person can sleep curled up in a ball without feeling cold. It's the edge, not the sweet spot.

The big number printed on the stuff sack is often the limit rating. So a "30-degree bag" may only be comfortable down to about 40. For fall nights in the 30s, many campers do best with a bag whose comfort rating is at or below the coldest temperature in the forecast.

02Your pad matters as much as your bag

Here's the mistake almost everyone makes. You crush the insulation under your body, so a sleeping bag does very little underneath you. The cold ground pulls heat out of you all night. That's the job of your sleeping pad.

Pads are rated by R-value, a measure of how well they resist heat loss. The higher the number, the warmer. A thin summer pad might be around R-2. For fall nights near freezing, aim for something in the R-4 range or higher. You can stack two pads too: a closed-cell foam pad under an inflatable one is a cheap, reliable upgrade.

Car campers: an air mattress is one of the coldest things you can sleep on. All that air gets cold. Put a foam pad or a blanket on top of it, between you and the mattress.

03Small tricks that make a big difference

• Eat before bed. Your body burns food to make heat. A snack with some fat in it before you turn in helps.
• Go to bed warm. Do some jumping jacks or take a quick walk before crawling in. A bag only holds heat; it doesn't make it.
• Change into dry clothes. The clothes you wore all day hold moisture from sweat. Sleep in dry base layers and wool socks.
• Wear a hat. A warm beanie at night is one of the cheapest upgrades there is.
• Fill a water bottle with hot water. Screw the lid down tight, put it in a sock, and drop it in the foot of your bag. Use a bottle rated for hot liquids.
• Pee before bed. Your body wastes heat keeping that water warm. And getting up at 3 a.m. in the cold is no fun anyway.
• Vent the tent a little. It sounds backward, but a sealed tent collects condensation from your breath, and a wet bag is a cold bag. Crack the vents.
• Pick your site. Cold air sinks and collects in low spots. A site a little higher than the valley floor, out of the wind, can be noticeably warmer.

04What not to do

Never bring a fuel-burning heater, stove or grill into a closed tent to warm it up. Every year campers die from carbon monoxide this way. If you want to use a heater, use one made and rated for indoor or tent use, follow its instructions exactly, and never sleep with a combustion heater running. We'll cover tent heaters in detail in a future post.

05The fall camping payoff

Get your sleep system right and fall camping is hard to beat: crisp mornings, coffee steaming over the fire, and a campground with half the summer crowd. Check the overnight low before you go, plan your sleep system for five degrees colder than the forecast, and you'll wake up ready for the trail instead of counting the hours until sunrise.

Sources (2)

OnePlanet: ISO 23537-1 temperature testing; Backpacking Light: Sleeping bag temperature ratings.

Photo: Camp - West Virginia - ForestWander by ForestWander, CC BY-SA 3.0 US.

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