10 Pro Tips For Staying Warm in a Sleeping Bag

By Michael Lanza

Head into the mountains in summer, or almost anywhere in fall or spring, and you can encounter nighttime and morning temperatures anywhere from the 40s Fahrenheit to well below freezing. That’s more than cold enough to pose a real risk of hypothermia or, at the least, result in a miserable night for you or a partner or child you’ve taken backpacking or camping—and would like to take more. Here’s the good news: The very simple techniques outlined in this article can turn a potentially unpleasant night into a comfortable one.

Countless frosty nights sleeping outside over the past three-plus decade—including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog—have taught me a few things about how to stay warm. (My coldest night was -30° F, in winter in New Hampshire’s White Mountains. I don’t recommend it.)

No matter how easily you get cold when sleeping outside, or whether you’re camping in the backcountry or at a campground, these 10 tips will keep you warmer on cool and chilly nights in your sleeping bag.

Tell me what you think of my tips, ask any questions, or share your own tips in the comments section at the bottom of this story. I try to respond to all comments.

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1. Clean Up

At the end of each hiking day, wash the dirt and dried sweat from your body; the latter can act like a heat conductor, chilling you, and getting a bit cleaner will just make you feel better. Swim in a lake, wade into creek and splash water all over yourself, or at least wet a bandanna or other cloth (or use wet wipes or other such products) and wipe yourself off.

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The Nemo Kyan 20 synthetic sleeping bag.
The Nemo Kyan 20 synthetic sleeping bag. Click photo to read my review.

2. Change Into Dry Clothes

Damp clothes promote conductive heat loss from the body. Change into dry clothing to sleep, as opposed to the clothes you sweated in while hiking.

3. Dress Smartly

Inside your bag, wear a hat, socks, and extra layers on your body, but avoid putting on so many layers that you isolate your core, which is your body’s furnace, from your extremities, which get cold more easily. It’s often more effective to wear just one or two light to midweight base layersthat are highly breathable, so as to allow your core’s heat to disperse throughout the bag. If you need more warmth, lay an insulation piece over your torso and hips inside the bag, essentially boosting the bag’s insulation, and stuff other extra clothing around you or at the foot of your bag to provide added insulation for your entire body.

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Feathered Friends Hummingbird UL 30.
The ultralight but very warm Feathered Friends Hummingbird UL 30. Click on the photo to read my review.

4. Use a Hot-Water Bottle

Stick a water bottle (like a plastic Nalgene bottle, not an insulated or vacuum bottle, which would not release any heat) filled with hot water in the foot of your bag. If that’s not enough, put a second bottle filled with hot water in the middle of your bag. Make sure they’re sealed tightly.

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5. Sleep on Insulation

Use an insulated pad or air mattress rated for the lowest temperatures you expect to encounter. Mats and pads with an R-value of between 3 and 4 are intended for three-season temperatures—generally, above freezing—while those with an R-value of over 5 are intended for use on frozen ground in below-freezing temperatures. If needed, add a second foam pad under your primary air mat if you’re sleeping atop frozen ground or snow.

Therm-a-Rest Hyperion 32F/0C sleeping bag.
The one-pound Therm-a-Rest Hyperion 32F/0C sleeping bag. Click on photo to read my review.

6. Augment Your Sleeping Pad

If you’re using a short air mattress or foam pad (to save weight in milder temperatures), lay your empty pack beneath your feet to insulate them from the ground, which can drain heat from your body even in summer. Or bring a short foam pad to provide more padding and insulation under a full-length air mat.

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A backpacker at a campsite on the Teton Crest Trail in Grand Teton National Park.
Todd Arndt at a campsite on the Teton Crest Trail in Grand Teton National Park. Click on the photo for my e-guide to backpacking the Teton Crest Trail.

7. Pile Extra Clothing Underfoot

Your feet get cold more easily than other body parts because they lie the farthest from your heart and, inside a sleeping bag, are not close to your furnace: your body’s core. They can also get cold because the ground under your sleeping pad is cold. Pile extra clothing under the foot end of your bag to give your feet more insulation against the cold ground.

Never get cold again (well, almost never).
See my “5 Tips For Staying Warm and Dry While Hiking.”


8. Use a Bag Liner

The Sierra Designs Nitro 800 20-Degree sleeping bag.
Testing the Sierra Designs Nitro 800 20-Degree in the Wind River Range. Click on photo to read my review.

Use a sleeping bag liner, which can add the equivalent of several degrees of warmth rating to a bag.

9. Eat Fat and Sugar (The Fun Tip)

Eat a snack high in fat right before bed, like a candy bar, and have a hot drink with sugar in it, like hot cocoa. Both will fuel your body’s furnace through the night.

10. Use Your Partner

If you’re sharing a tent with a partner who doesn’t get cold as easily as you, ask that person to sleep on the tent’s windward side. If you have two warm-sleeping partners, sleep between them, or at least position your bags and pads close together to benefit from one another’s body heat.

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Leave a Comment

27 thoughts on “10 Pro Tips For Staying Warm in a Sleeping Bag”

  1. I like an external cover over to slide my bag into this keeps the outside moisture and frost from settling directly on your bag’s surface.

  2. Michael,
    My husband I recently returned from a challenging (for a couple of almost 65-year-olds) backpacking trip in Yosemite, a trip which would not have happened if I had not read your post on getting a last minute permit: many thanks for that! Your post “First 5 things I do in camp” was also valuable in increasing our comfort and readiness for the next day’s effort.

    We spent several nights near or just over 10,000’, and I was cold in the early morning hours. Not sure what the exact temperature was, but when we departed the forecast for Tuolumne Meadows (8,600’) was lows in the upper 20s.

    I’m now evaluating whether there are steps I can take to ensure my comfort on late summer/high elevation trips or if it’s time to update my 2014 REI Joule 23. I just read over your post with tips for staying warm in a sleeping bag (I did many but not all the tips) as well as your 2021 review of sleeping bags and have a couple of general questions as well as more specific questions about one of the recommended sleeping bags.

    1. In terms of “dressing smartly,” you mention wearing a breathable baselayer to allow core heat to disperse. As I got chilly, I pulled on my Nano Puff jacket and hood rather than draping it over my torso. Was that the wrong approach?

    2. My feet were cold despite wearing clean wool hiking socks. I had a seat pad under my feet and extra clothes inside my bag under my feet. Do you think wearing down booties is an effective approach?

    3. I’ve read that a sleeping bag with a draft collar will be warmer than one without it. My current bag does not have one. In considering the Feathered Friends Egret UL 20 that you recommend, I notice it lacks a draft collar and instead has a “passive collar with an extra cushion of down.” From your experience, does the design of the Egret essentially work like a draft collar?

    3. The Egret comes with continuous baffles. Is there a downside to this design? Are cold spots more likely if the down has not been evenly distributed? Might a side sleeper who switches from side to side during the night shift the down and create cold spots?

    4. How does the length of the sleeping bag affect warmth? I ask because my height is 5’ 6½” and many women’s bags use 5’ 6” as the break between a small and regular sized bag (or regular and long). I do tend to have cold feet in general. Is it best to go for slightly long or short?

    I have found valuable information in many of your posts and appreciate any guidance you may be able to provide me. I understand if you think my specific questions about the Egret UL 20 should be answered by Feathered Friends.

    Thanks for your tips and inspiring work,

    • Hi Karen,

      Thanks for your kind words about my blog, I’m delighted you find it helpful in many ways, specifically this story and my tips on getting a last-minute Yosemite wilderness permit and my story “The First 5 Things I Do in Camp When Backpacking.”

      Thanks also for your good question. The first piece of advice I’d offer is that you probably just need a warmer bag for the temps you encountered in Yosemite—with a forecast for lows in the upper 20s at 8,600 feet in Tuolumne Meadows, you certainly would have pushed the comfort range of your REI Joule 23 at 10,000 feet, even if you don’t get cold easily. The Joule 23 is a decent bag, but I suspect many people would find it inadequate for temps lower than the upper 20s Fahrenheit.

      The Feathered Friends Egret 20, on the other hand, is among the very warmest bags in that temp rating range, speaking from my experience with the men’s version, the Hummingbird 30, which has kept me warm in temps at and just below its rating. Besides having the highest-quality down available (950-fill), FF packs those bags with more down than you’d find in many similarly rated competitors. Lay the Egret 20 beside the Joule 23 and you’d see a visible difference, I think. I suppose FF calls it a “passive collar” because it’s not a flap like a draft collar, but nonetheless, the bag closes up snugly around your neck and face to trap heat. The Egret also has extra down in the foot box. Continuous baffles can allow down to shift a bit, but I’ve never experienced cold spots in my Hummingbird, perhaps just because it’s stuffed so fully, and I’m also a side sleeper.

      The Egret medium also has a length of five feet, nine inches, just about perfect for you. A bit of extra length is good, allowing you to pack extra clothes under your feet and at the end of your bag. But if it’s too much longer than your body, the foot box will become a cold spot that you’ll notice when fully extending your legs. Greater bag volume overall also means your body has to warm a larger space, which can compromise your warmth.

      You followed many good practices for keeping your feet warm—short of putting a tightly sealed bottle filled with hot water inside your bag (or two, one near your stomach and one at your feet)—which also leads me to believe your bag simply wasn’t warm enough.

      Pulling on a down jacket (or other non-breathable insulation layer) inside your bag will boost heat to your torso, but also trap it around your torso; and because your core is your body’s heat producer, the down jacket blocks that heat from circulating throughout your bag to help warm your extremities. It’s less of a problem for hands, which are close to your torso, than feet, which are farther away. Once your feet get cold, it’s hard to reward them, especially because your brain will cut off blood circulation to cold extremities to protect the vital organs (called vaso-constriction).

      That’s why I’ve always found it more effective to wear just breathable layers inside a bag, including a warm hat and socks. I’ve spread a down jacket out over my body inside a bag and felt it deliver a fast boost of warmth that spreads throughout my bag, including to my legs and feet. Down booties may help warm your feet and will be more effective if you pull them on while your feet are warm; if they’re already cold when you put them on and then immediately crawl inside your bag, you might isolate your cold feet from your body and delay their warming.

      I hope that helps. Thanks again for the good questions and get in touch anytime.

  3. All good suggestions. I have an additional one: Wear a knitted hat to bed. We loose a considerable amount of heat though our heads. This always works for me.

  4. +40 years recreating and rescuing others in Wyoming winter mountains. I thankfully still have my fingers and toes using lighter fluid type pocket heaters (zippo). They last for up to 10 hours and are bombproof. Mother Nature WILL spank you if you are stupid in the cold.

    • Thanks for the good suggestion, Rak. In my experience, people often make mistakes in the backcountry not because they’re stupid but because they’re inexperienced or uninformed in some skill or environment, and sharing information is, hopefully, the way to avoid bad outcomes.

  5. Great article and all good comments. My additional go to: Load your coffee pot up the night before with water and coffee in case your water you may have left at less than 32 degrees freezes. And yes, that has happened to me and it is not a happy morning sight.

    • Tip #9, eating before going to bed… while the rare occurrence likely will have no observable effect, please Google and reference articles discussing the effect of sugar and digestion time lapse upon the brain as relates to Alzheimer’s and dementia.

      As always, thank you for your articles and insights, helps me get through the day while waiting for the next opportunity to visit The mountains.

      • Thanks, Edward, I’m honestly not familiar with any research or data behind sugar, Alzheimer’s, and dementia. I’m simply suggesting that consuming fat before bed when camping in sub-freezing temps has always given me a long-lasting boost in warmth, much as consuming fat boosts warmth and energy when I’m active during the day in sub-freezing temps.

  6. Michael,

    Great tips. A few that work for me. I carry wet ones for clean up, especially when it is cool/cold or at elevation. I carry down booties for those same conditions. They are light but great warmth.

    When buying a bag make sure it is not too tight fitting because it is more difficult to use a liner or add layers. Or too large as there is too much space to warm.

    Head wear can vary from light, medium or heavy. Same with liners.

    For cold trips take a pee bottle. Make sure it is marked or an unique shape. Close it tight.

    If you can, shift your down (if you have a down bag) to the top and sides. When you lay on the down it compresses loosing most of its insulation value. Better yo use that second pad, clothing, your empty pack, etc that you recommend underneath.

    Avoid or minimize the amount of condensation. Similarly avoid/minimize perspiring. Moist down does not insulate as well. Also, dry your bag whenever you can. Even in cool/cold weather keep your tent ventilated.


  7. So I have a crazy-pants tip to add to the list I swear had worked for me: No matter how cold and uncomfortable it is outside, make sure to completely empty your bladder before going to sleep. If you need to go in the middle of the night, do it. Don’t hold off until morning.

    My pseudo-science theory as to why this seems to work: instead of your body working hard to keep all that pee at a toasty 98 degrees, it can use that energy to keep the rest of your bits warm.

    Take it or leave it . But I’ve decided a few seconds of cold booty is worth hours of greater warmth in my bag.

    • Thanks, Jes. I first heard that tip years ago. I’ve debated it with friends who have science backgrounds and insist that the body would not burn any more energy heating urine that’s inside the body that’s at body temperature, anyway. My take is that staying well hydrated certainly helps keep you warm, and I relieve myself right before bed in hopes of not having to get up during the night; but if I have to, I do get up, because it’s hard to sleep otherwise. Keep a warm puffy jacket handy to slip on if you have to get up.

  8. I use Coleman Trinidad warm weather sleeping bag (http://campingandcamping.com/coleman-trinidad-sunridge-warm-weather-sleeping-bag-review/) for my summer camping trips.

    For colder weather I have two more sleeping bags. One is a 3-season sleeping bag, another one is a 4-season sleeping bag.

    There is definitely no need to spend 300 or 500 USD for a summer sleeping bag. Don’t get fooled by the “amazing features”. A warm weather sleeping bag can be as simple as it can be…

  9. I usually don’t have much of a problem staying warm since I use a nice down bag, but our kids, 4 months and 2.5 years get cold. We usually try to have them sleep near mom and haven’t stepped out to get them their own little bags yet.