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.


Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-guides to classic backpacking trips. Click here to learn how I can help you plan your next trip.


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

4. Use a Hot-Water Bottle

Stick a water bottle 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 and that you’re using a sturdy, plastic bottle that’s designed to hold hot liquids, like a Nalgene bottle; a cheap plastic bottle (like an empty soda bottle) could split open, a potentially very dangerous situation. An insulated or vacuum bottle would not release any heat, negating any benefit.

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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.

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The Mountain Hardwear Bishop Pass 30 in Yosemite.
The Mountain Hardwear Bishop Pass 30 in Yosemite. Click photo to read my review.

8. Use a Bag Liner

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.

See my “Pro Tips For Buying Sleeping Bags” and all of my reviews of sleeping bags, air mats, and backpacking gear at The Big Outside.

Whether you’re a beginner or seasoned backpacker, you’ll learn new tricks for making all of your trips go better in my stories “How to Plan a Backpacking Trip—12 Expert Tips,” A Practical Guide to Lightweight and Ultralight Backpacking,” and “How to Know How Hard a Hike Will Be.” With a paid subscription to The Big Outside, you can read all of those three stories for free; if you don’t have a subscription, you can download the e-guide versions of “How to Plan a Backpacking Trip—12 Expert Tips,” the lightweight and ultralight backpacking guide, and “How to Know How Hard a Hike Will Be.”

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

  1. All great info.
    Some other tips is use a four season tent vs a three season.
    Use an insulated pad vs air mattress.
    Use a high quality sleeping pad and bag like wiggy’s brand. Best bag out there hands down.
    I froze my a** off in the boundary waters in northern MN at 24 degrees w a bag rated for 10 degrees. It didn’t help all the clothes I put on were mostly cotton. Woke up freezing. From that trip stemmed everything quality I now own. Bag. Tent. Pad. Didn’t know there was a diff between 3&4 season. Etc. clothing types vs cotton. Wool socks. Etc.

    Reply
    • Thanks for sharing those suggestions, Steve. I mention the insulated air mattress above, which is important even on most summer trips in the mountains and I have spent many frigid nights outside in winter (and wrote a how-to guidebook about winter camping). I agree about the value of high-quality gear, including bags, although I have used many bags that I consider excellent and I would respectfully not agree that Wiggy’s makes hands-down the best bags out there. See this menu of all sleeping bag reviews at this blog.

      Reply
  2. Hi
    I’m a beginner 😁
    Just just a week camping at the foot of mount snowden in wales. I was told that if you wear as little as you can this will be more effective
    Thank you

    Reply
    • Hi Wayne,

      That advice can be generally true because wearing just some base layers helps the warmth created by your body’s core (its furnace) allows that heat to fill the entire bag, warming your extremities, rather than trapping all that core heat inside, for instance, a puffy jacket when in your bag. It’s also just naturally more comfortable to not wear a lot of layers when sleeping. I usually wear socks (my feet get cold easily), a short-sleeve or long-sleeve top, and underwear, plus a hat when needed. But if your bag isn’t warm enough and your body’s core gets cold, your only option for warmth is to add layers. Thanks for the comment.

      Reply
  3. Hi Michael, What degree bag do you typically use in the Sierras in late August and September, say on your Sequoia Mineral King hike or on the JMT? I have traditionally used a 30 degree bag with sometimes a silk liner, and if it gets really cold I wear lots of clothes inside. But I am considering making the move to a 20 FF degree bag. Any advice you can give would be appreciated.

    Reply
    • Hi Jeff,

      I personally don’t get cold too easily—which makes a difference—and I’ve always used a 30-degree bag through September in the Sierra, sometimes even into October. I’m going this August and will definitely use a 30. I agree that it’s easy enough to supplement with clothing layers if needed, but I’ve never needed more than a hat, socks, and one base layer top and bottom, rarely even all of those. Bring an air mattress with an R-value of 2.5 to over 3 for three-season temperatures.

      Reply
  4. Michael, Lately, I’ve been using a heated vest that I turn on when I get in my sleeping bag . I turn it off after about 10 to 15 minutes and stay warm all night. It is light weight and uses the same power source that I use to charge my phone etc. Works well for me as I am a cold sleeper.

    Reply
  5. Just one word of warning re Item 4 – make sure you use “Hot Water”, NOT boiling water. I am recovering from very painful 2nd and 3rd degree burns after a normal, fairly new hot water bottle split after filling (although this may not be an issue with Nalgene ?)

    Reply
    • Hi Anthony,

      Sorry to hear about your accident, that’s horrible. Thanks for sharing it to alert other readers. Yes, you do have to use a sturdy plastic bottle that’s designed to hold hot liquids, like a Nalgene bottle. Good luck with your recovery.

      Reply
  6. Here here to tip 9, heehee! In all seriousness, thanks for the thorough and helpful article! I have experienced the benefits of the hot water tip first hand and was so grateful someone showed me (we used large Mason jars but good to know other bottles work).

    Reply
  7. Hi there,

    I like most of your tips and actually for first time borderline freezing temp novices – this advice couldn’t be better! Safe, simple smart and no shi shhhh bologna.

    However, I’ve slept in sub-freezing temperatures backpacking in a field (baddddd choice with my summer tent) and survived backpacking where not many people usually wander. Most are climbers doing the cold weather thing. Well either I’ve grown entirely impatient, bored out of my mind or I’ve gone completely mad because I’ve decided I can’t wait anymore for spring and during our Minnesota snowstorms I’m going to try what I call board backpacking (snowboarding and backpacking) which means hiking to the top of a remote location with snowboarding gear with the intent of hunkering down for the storm and when it’s done… Boards on, I’m out ripping down the fresh powder. Completely and utterly alone (besides my dog).

    The climates breaking down we have -30 windchill and that’s as good as it’s going to get. I have to deal with it or stay home.

    My question to you is: gear. How does one 135 lb girl and her not-snow dog stuff that much gear into a sled/backpack for 7 days and keep it light, keep it warm, keep it real?

    I heard Tyvek makes for great insulation outer bivy layer?

    Reply
  8. I put a couple of handwarmers in a sock and place them in the middle of my sleeping bag. They give off heat for about6 or 7 hours.

    Reply
  9. I think your advice is spot on. I am a winter hiker and never suffer from cold, following the simple steps you have outlined here. I especially agree with the clothes and gear under your feet! Well done.

    Reply
  10. 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.

    Reply
  11. 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,
    Karen

    Reply
    • 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.

      Reply
  12. 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.

    Reply
  13. +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.

    Reply
    • 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.

      Reply
  14. 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.

    Reply
    • 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.

      Reply
      • 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.

        Reply
  15. 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.

    Cheers

    Reply
  16. 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.

    Reply
    • 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.

      Reply
      • Water conducts heat 25 times better than air. It would stand to reason then, that a full bladder will suck more of your body heat than an empty one. And I have plenty of real-world experience to form my opinion. I almost always ‘go’ before bed (even at home) but on the occasions that I wake up in the backcountry at night, I virtually always find myself cold AND having to pee. The internal debate always rages about being able to hold it until morning, but invariably I always end up thanking myself by falling right back asleep, warm and comfortable, after making the right decision.

        Reply
        • Hi Matt,

          Thanks for sharing those thoughts. I’m no scientist but I think your calculation about the completely true fact that water conducts heat better than air as proof that a full bladder drains precious calories/heat from your body overlooks a key fact: The bladder isn’t surrounded by air or independent of your body, it’s within your body. Plus, you could be waking up cold for reasons entirely unrelated to the fact that you have to pee (which is common if you wake up at night warm, too).

          Reply
  17. 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…

    Reply
  18. 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.

    Reply