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The Science of Clothing Layers for Winter Hiking

The Science of Clothing Layers for Winter Hiking

Wearing multiple clothing layers for winter or cold weather hiking keeps you drier and warm by moving moisture away from your skin. Sounds simple, right? It is, but many people struggle to understand the scientific principles behind layering and how they can guide your baselayer and mid-layer clothing choices for winter hiking. Check out our clothing recommendations below.

Layered Clothing

The core principle behind layering is to dress like an onion, with multiple clothing layers playing different roles in moisture management, heat retention, and weather protection.

  • Baselayer garments are worn directly on your skin and are designed to keep you dry by moving perspiration to the next higher layer, your mid-layer.
  • Mid-layer garments are designed to keep you warm, even though they absorb moisture from your baselayers. Some mid-layer garments are more breathable than others and can dry when worn, while others are designed purely for warmth and are not terribly breathable. We discuss this further below.
  • Finally, an outer shell layer is designed for weather protection, be it wind, rain, or snow.

Evaporative Cooling and Wicking

Baselayer clothing is intended to move moisture, created through perspiration, away from your skin in order to counter a physical process called evaporative cooling. When moisture sits on your skin, it literally sucks the heat out of your body in an attempt to evaporate. This is the reason why perspiration makes you feel cooler in summer.

In winter, you want to move that moisture off your skin and through your baselayer clothing so your skin isn’t in contact with wet fabric. That’s where a mid-layer comes in. The best mid-layers will absorb the moisture passing through your baselayer garments. This is a process called wicking. Ideally, you want a mid-layer that remains warm when it absorbs moisture or multiple mid-layer garments that achieve the same effect.

The underlying mechanism behind wicking is called capillary action, where a liquid is pulled from one layer to another without the influence of gravity. If you’ve ever dipped the corner of a sponge into a pool of water, the water is drawn into the sponge through this process.

The strength of the wicking process between a base layer and a mid-layer depends on the structure of the mid-layer and how absorbent it is. A porous mid-layer, like a fleece pullover, is very effective in pulling moisture out of a baselayer garment because it contains many small pores that suck in moisture like a sponge.

The outermost layer, a shell is usually the least wicking layer and is designed more for wind, rain, or snow protection. It may passively trap some of the warm air that escapes the mid-layer, but it’s usually not insulated.

Dress like an onion, putting on layers when you get cold and taking them off when you get warm.
Dress like an onion, putting on layers when you get cold and taking them off when you get warm.

Clothing Selection Guidelines

Here’s what the science of layering informs us about clothing selection for winter hiking. If you like wool, you’re really going to hate what I’m about to tell you. 


The best baselayers are ones that don’t absorb much perspiration and which can wick it efficiently to your mid-layer. Synthetic jerseys and long underwear are clear-cut winners on the score. Thinner baselayer garments are better than thicker ones because the moisture has less distance to travel to your mid-layer. The same holds for more fitted baselayers versus looser-fitting ones. If you can hold up a baselayer jersey and see light coming through it that’s good. It’s even better if you can see the outlines of objects or furniture in the same room.

Synthetic baselayers hold up very well over time, they’re inexpensive and easy to launder in washing machines. My gotos are REI Active Pursuits Long Sleeve T-Shirt, Nike Dry-Fit Legend Long Sleeve Tee, Helly Hansen LIFA Stripe Crew, and the Helley Hansen LIFA Pant.

Wool baselayers hold onto moisture and take much longer to dry, even though they can feel warmer when they’re damp. As far as layering goes, the primary goal of a baselayer isn’t to keep you warm but to move perspiration off your skin to the next layer. I know people like wearing wool baselayers because they don’t smell as much, but I’m much more interested in wicking performance than body odor on winter hikes when icicles hang off my nose hair and beard.

Wool baselayers have other issues too, such as high care and maintenance requirements (special soap, hand wash, hang dry), and they have to be replaced much more frequently than synthetic base layers. They are also a lot more expensive. I’m lucky if I can get two years out of a wool jersey, while I can easily get ten years or more out of synthetic ones. That’s a lot less trash in the landfill with none of the associated overhead of animal husbandry.

Wool baselayers made with a combination of wool and synthetic yarns are a better choice than straight wool and there is a whole segment of the outdoor industry working to make wool suck less. Some good examples include  Smartwool Intraknit, Ortovoz Comp Light, Helly Hansen LIFA Merino, and the Nuyarn garments made by KUIU and Artilect.

Fleece hoodies and vests are the bread and butter of winter mid-layers
Fleece hoodies and vests are the bread and butter of winter hiking mid-layers


Fleece mid-layer pullovers and hoodies are better than wool because they dry quickly when exposed to air. The problem with fleece is that the outdoor industry has come up with so many proprietary variants that it’s impossible to know how well a garment will perform unless you try it in the field. Gone are the days when all fleece was classified as being 100 weight, 200 weight, or 300 weight and you knew exactly what you were getting.

If you want a 100-weight fleece or a close approximation, which is usually quite sufficient for active hiking or snowshoeing, the inexpensive fleece pullovers or jackets from REI, Decathlon (size up), The North Face, and Lands End are often your best bet.  My goto fleece hoodies are made by Ragged Mountain Equipment in Glen, NH a few miles from my home. Go to the store for the best selection as their website sucks. They have really unique clothing. Fleece vests are also a great mid-layer because they are very effective at keeping your core warm, but your arms cooler, and they can be vented in front.

Wool mid-layers can also be suitable as mid-layers, including hoodies, although they wick and dry somewhat slower than their synthetic counterparts. I’ve had the most experience with wool pullovers and hoodies from Minus33 which is another New Hampshire brand, which my friend Wanda also likes. While they hang in my closet, they’re just too warm and heavy for me to wear often. Still, they may be a good option if you run cold.

Many hikers seem to think that insulated synthetic and down jackets make good mid-layer garments. While they are good passive layers to throw on if you take a break and want to ward off a chill, they make remarkably bad active mid-layers because you’ll be too warm if you try to hike in them, you’ll sweat like a pig, and soak your base layer and the jacket liner. You are much better off wearing cooler layers that will keep your baselayer and mid-layer insulation drier for the entire day. Winter hiking and snowshoeing generate a huge amount of body heat and you’re not going to be cold if you’re moving. But don’t take my word for it. Go try it. That’s how everyone learns what they prefer when it comes to layering winter hiking clothes.

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  1. Good article – I always learn something. Thanks

  2. No mention of the alpha direct garments in this article. How do you like to work them into layering? I’m experimenting with a Senchi Lark for this first time this winter, and I read your review on the Farpointe. I originally thought of it as a mid-layer, but it seems to throw all my prior experience with base layer + fleece layering out the window. In temps below freezing, I used an OR Foray jacket with it and regulated my warmth with the pit zips. Used alone, with no other layer other than the jacket, the Lark performed beautifully. I was dry and warm – or cool, when at higher elevation and colder temps. I’d much rather be slightly chilled than hot and sweating of course. Then I tried it with a capilene lightweight t-shirt as a base layer, on a slightly colder day. The capilene was soaked at the end of the day, and I could tell because I was cold when I opened the pit zips and the wind blew. Is alpha direct the ultimate all in one, replacing a base & mid layer in a single garment, turning the traditional 3 layer system into 2 layers?

    • I haven’t found a compelling use for alpha direct in winter yet. It has no wind resistance compared to a power stretch fleece so you can’t wear it over a baselayer by itself. If it replaces anything, it will replace mid-weight puffy when its coupled with a hooded wind shirt. But it doesn’t absorb much moisture from a baselayer because it’s so porous, so what good it is as a wicking midlayer? You have to understand, alpha was never intended to be use used as a standalone garment but as a component in a multi-part item.

      • Interesting. I found it worked very well by itself in 10s-20s with a shell that has active venting such as the OR Foray, as long as I was moving. Open the pit zips when climbing, close when descending or on level terrain. Throw my EE Torrid on over the Foray at breaks, and I was plenty warm. I am anxious to see how this system fares as temps approach 0. Or with a more beathable wind jacket such as the BD Alpine Start. Perhaps it will not provide enough warmth when not working hard. I have been carrying the traditional base layer + fleece system in my pack as a backup. Your point about lack of moisture absorbtion is probably why I was left with a soaking wet base layer.

        • Actually, it sounds like you are overdressed (too warm). I almost never wear a hard shell even though I carry one. I do use a BD Alpine Start most of the time, but even then I have to take it off to avoid sweating unless it’s really windy. But when I take it off again, my fleece mid-layer dries quickly. Keep experimenting. it’s really the only way to dial in a system you like. Whatever you do, just know that a soaked baselayer is not a good thing. You don’t want your skin to be wet. You want to take clothes off (delayer) to avoid that. Release excess heat.

      • It’s a replacement for a 100wt fleece midlayer. More warmth for less weight, better packability, and much better breathability. I normally hike in a just a windshirt (Alpine Start is my fave as well) and Capilene Thermalweight base down to around 20F, below that I used to add a 100wt fleece midlayer. Problem is even in the teens I would start to sweat after a few miles. Replacing the fleece with Alpha Direct 90 solves that problem – I can be warm down to 0F yet still not sweat at 30F. The downside is it can ONLY be used as a midlayer, you can’t use it as an outer layer like you sometimes can with traditional fleece because it has zero wind resistance and snags easily. If you’re finding yourself having to take off your Alpine Start due to sweating, try replacing your fleece with AD and I bet the problem goes away.

        • Scratching head. Why would you want to wear a third wind layer just to wear an AD fleece. Sounds like you’re jumping through hoops to justify using a garment that is less multipurpose than a simple 100 weight fleece, which is cheaper and much easier to care for. Alpha stinks when you sweat in it and then you have to hand wash it because it’s so delicate.

        • Philip – I think you misunderstand me. There is no third wind layer. Baselayer->Alpha Direct Midlayer->Windshirt. That’s it. The AD replaces the 100wt fleece. You can machine wash them, you just put it in a mesh laundry bag ($8 on Amazon, some Alpha sellers give them for free with your purchase) and throw in the washing machine.

        • That’s 3 layers. I didn’t misunderstand you at all. An AD does not replace a 100wt fleece. The 100 wt fleece is much more windproof and can be worn by itself over a baselayer.

  3. “The 100 wt fleece is much more windproof and can be worn by itself over a baselayer.”

    Not for me: “more windproof” is not really windproof – which I feel badly, if the wind is blowing hard.
    But I get what you mean! Not all men are created equal in their thermophysics and some like it more breathable like you, (probably because they are sweating faster), some need more wind protection and for them the classic fleece under the windshirt is to warm.

    • Look – the secret to layering is to experiment on yourself. No amount of internet chatter can replace experience. Try different stuff in different conditions.

      • true that. the pinnacle store would have rooms of different temperatures and let you work out, sweat, try gear out.
        maybe I’ll pug my nose and open a store and charge quadruple

      • all jokes aside IFeel, a discussion without “pairing” or experiencing
        1. activity/activity level (including gain and load bearing)
        2. biological fact: body composition, sweat prod variance; maybe fitness level
        3. conditons/weather: temp, %humidity, altitude,
        4.duration/recovery: how long is the activity; how long until time to R&R, launder, or at least give gear a chance to sun/air dry

  4. Informative article–I enjoyed reaidng it!

    I wanted to add that Duckworth is a company that makes both 100% wool and wool-blend garments. They provide the best wool garments/gear that I have owned, so far. Just wanted to mention them–and their clothing is completely U.S. produced; sheep grown, wool sheared, woven and garments sewn within mainland U.S.A.

    Side-note, one doesn’t need to use specific soap to launder wool garments. Additionally, due to the anti-microbial properties of wool, it resists odors, so laundering is needed far less frequently, and saves water. I’ve also found that relatively lighter wool basewear dries quickly when hung to dry. I do agree that heavy wool sweaters, on the other hand, generally need more drying time.

    Well, thanks again for your highly informative article.
    Take good care!

  5. Those of us who are “po’ folk” (and cannot afford a lot of the newer fibers and fabrics) often rely on synthetic base layers from Wally World and wool mid-layers from (GASP!) the local thrift stores. Granted, I would NEVER think about winter backpacking in the Whites or some of the higher peaks in the Adirondacks or the Catskills using this stuff, but for lower elevation excursions (day hiking, backpacking, dog-sledding), it works quite well, doesn’t cost a lot, and is INFINITELY BETTER than cotton “waffle” thermals and jeans – which I still see in the winter in alarming profusion, in both NY and Pa.

  6. I am trying out a Brynje fish net base layer top with a Norrona Lyngen Alpha 90 Jacket with a wind breaker to snowshoe this year. As a sweat hog is the most breathable set up I can find so far. Worked well in 20 degree weather.

  7. Another good article from a qualified authority. Thanks Phil.
    ->As a long time Nordic Ski Paroller and winter camper I relied on polypropylene then polyester for base layers and still prefer polyester base layers over Merino wool.
    ->Then came polyester fleece like Polarguard which was great for XC skiing and other active winter sports.
    ->But down was and still is the warmest-for-weight.
    NOW I ONLY BUY DOWN GARMENTS AND SLEEPING BAGS WITH DWR TREATED DOWN. (My most indulgent down garment is a -30 F. expedition parka from Eddie Bauer but when it’s bitter cold it is THE answer.)
    ->I recently bought a KUIU rain parka of the Japanese Toray Industries WPB laminate and it does breathe better than anything but eVent.

  8. Philip, could you do an article on face masks and goggles for sever cold and winter wind?
    (And maybe for winter camp sleeping too.)

  9. Any thoughts about “micro-climates”? I use a wind shirt over a basel-ayer, or over a fleece layer, and then throw a shell, or puffy jacket, over that. I find it works really, really well, and adds flexibility as well as about 10ºF of warmth (for me).

  10. I’m amazed there isn’t a mention of mesh.

    • I talk about mesh all the time. It makes an excellent baselayer too. Warm and wicks great. But I only wear it when it is really cold. Even then I prefer synthetic Brynje shirts, although they also make them in wool.

  11. all jokes aside IFeel, a discussion without “pairing” or experiencing
    1. activity/activity level (including gain and load bearing)
    2. biological fact: body composition, sweat prod variance; maybe fitness level
    3. conditons/weather: temp, %humidity, altitude,
    4.duration/recovery: how long is the activity; how long until time to R&R, launder, or at least give gear a chance to sun/air dry

  12. Great article, thanks! What do you recommend for legs as that is where I get cold?

    • While you could try long underwear, which is what a lot of my female friends wear all day, I find that way too hot. I usually wear softshell pants that keep me warm enough down to about 10 degrees and layer over them with rain pants that have side zips for ventilation if I start to run cold. Air is the best insulator and you’d be amazed at what a difference a shell layer can make. If you try that make sure you get rain pants that can be taken off and put on without taking off your boots, so you’ll want high ankle zips at a minimum. Another alternative is to get long underware that have full length side zips and can be taken off if you get too warm without first removing your pants. Check out the live demonstration in this article.
      You may also find this article about pant layering useful.

      hope that helps!

  13. Philip, thank you! for writing and posting this: simple and clear advice at last. I have never been able to make sense of sometimes contradictory layering guidelines. I think the marketing of these garments adds to the confusion. Much appreciated.

    • I think the big problem is that clothing layers are designed for downhill resort skiers who sit on their butts half the day and thats who the big brands sell to. Winter hiking is a totally different kettle of fish. Glad you’ve found this useful.

  14. I have used 100% merino wool base layers exclusively for 20 years for both winter and summer trekking in Alaska. I can sweat profusely at times but have never had issues with becoming soaked or getting hypothermia. The key is to be diligent about adjusting layers as you warm up or cool down and BEFORE you start to sweat. I find that merino wool has a much wider temperature comfort range than synthetics, and during a two-week trek in the backcountry where no shower is possible, its odor-resisting ability is a major advantage, because I can wear them comfortably as sleeping layers without being overpowered by my own funk. They also seem to help keep my non-wool outer layers from getting too stinky. They require no special care and go into the washer and dryer with my other clothes. Some items have developed small holes over the years but they are still fully functional and I have not had to dispose of anything yet.

  15. Great article. Now I understand why my thin base layer is actually warmer than my thicker base layers! When I mountain bike in the winter I would wear a thin base layer, with a somewhat thin wool top and be fine the whole time. If it was REALLY cold and windy I would add a windbreaker VEST. One thing to remember in winter, keep your feet warm!

  16. Exactly! Base, insulate, wind. Then I have a thicker insulate + wind for when I stop. No changing. Just layering.

  17. Layering is not just for winter … it’s a practical practice even in summer. Cold weather layers sometimes 4 w/out outer shell; summer layers – usually two unless way hot.

    Base = technical material
    2nd = UV hoodie or merino depending on season – both hooded
    3rd = lightweight fleece
    4th = out shell – water / rain, unless way cold and then a heavier fleece over lightweight (<20 degrees)

    Finding what works best takes practice as everybody's body works at different temperatures imho.

  18. Informative, as always. Thanks Philip. I visit this site most days, always picking up useful info.

    I’ve been looking for an ‘active’ synthetic layer to use in winter for temps between 0C and -20C. This would replace my fleece mid layer + windproof.

    Initial contenders were Rab Xenair Alpine Light, Rab Vapour Rise Alpine Light, Patagonia Nano Air and Patagonia Thermal Airshed.

    I was hoping an active synthetic jacket would keep me comfortable when working hard and warm when going slow, but it seems you’re not keen on this approach or have I misunderstood?

    I would love to read more on thoughts and experiences regarding this type of ‘active’ Synthetic layer.

    • I guess it depends on how cold it is and how slow you go. I have a Rab Xenair Alpine Light and while I like it for standing around, I drench the inner lining when I try to hike uphill with it in 30 degree weather while wearing a backpack. Try it for yourself.

      • Hiking uphill at temps under 30F (-1C) is actually the use case I’m looking at.

        I’ve not found anything to suggest the approach I was looking at will work. I’ll check in the sales to see if I can find a bargain but will stick with what I’ve got for now.

        Thanks for your input. Have a good one ???

  19. An interesting article with some good advice about what to wear, but it does not get the science of clothing layers quite right. The idea that you can sweat into your clothing and not pay a price if you have technically layered your clothing properly is not true. In winter hiking there can be a price or penalty to be paid for becoming overheated and sweating into your clothing. This price is a loss of body heat. (not to mention the increased risk of dehydration)

    When the base-layer wicks moisture off your skin (thru capillary action) and moves it into the mid-layer insulation this can stop the evaporative cooling from you skin, but unfortunately the story does not stop there. Once the moisture arrives in the mid-layer it either evaporates or remains as moisture. If it evaporates, where does the heat that evaporation requires come from? It comes from the only heat source: your body. If it does not evaporate it remains as moisture and reduces the R value of the mid layer insulation. The degree of reduction depends on the nature of the material. Layering does not make this fact irrelevant (regardless of how we may feel about it.) In either case there is a negative impact on your body’s heat retention, and it can be dangerous if the temperature drops or it you are spending the night outside while depending on your clothing for warmth.

    The only way to prevent this negative impact is to not sweat by not overheating. Few people know how to do this, but the ability to sense when you are beginning to overheat and immediately remove insulation to prevent sweating can be learned. Layering should make it easier to put this into practice, but making misleading inferences about layering reduces the incentive to learn this important winter skill. The proper conclusion is that sweat and wet clothing in the winter is a bad idea in all circumstances and should be prevented by preventing overheating in the first place. Layering is never a free pass to sweat in the winter.

    The article states, “The primary goal of a baselayer isn’t to keep you warm but to move perspiration off your skin to the next layer.” This idea assumes that perspiration can’t be avoided, which isn’t necessarily true. The body is smart, it only sweats to cool an overheated body. Avoid overheating by mentally monitoring body temperature and selecting an appropriate level of insulation. To me the baselayer is definitely chosen for insulation value because I avoid sweating by delayering.

    • Delayering is vital, but you’re mistaken in thinking that moisture can’t evaporate without body heat. It dries by evaporation the same way that your clothing dries when you hang it up. Just take off your outer shell.

  20. I’ve had good success with the shelled alpha garments. OR used to make one called ascendant. The rab alpha direct is my go to for ice climbing and really cold hiking. It’s warm over at shirt; maybe alpha 120. The wool synthetic blends by Patagonia and Helly are awesome. The Patagonia nano air light hybrid hoody is the best winter garment I have ever worn. Ridiculous name and they discontinued it. Great for high output in a large range of temps.

  21. I truly enjoy reading your reviews and opinions. Over the decades, I have tried several (mostly low cost) options. I realized that West US cold vs East US cold can add more variables (Rocky Mountain wind speed?). I tend to view internet chatter as opinion without enough context if the environment and activities aren’t mentioned. Anything can work for anyone “best” in the right conditions and no one needs to argue about it. My cold weather gear in the Rockies is a little different than what I wear here. People should just practice, have fun, and use whatever works for them.

  22. Phil,

    Would either of these two make a good baselayer? And lastly is a Patagonia R1 hoody a good mid layer? It works well for me in colder weather and shoulder season but just curious if you recommend it?



  23. Capilene is a good base layer. Yes the R1 hoody is a bomber mid-layer.

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