Winter Hiking in a Thin Baselayer

Winter Hiking in a Thin base layer

The biggest mistake that new winter hikers make is overdressing by wearing heavy or medium-weight baselayers that are hard to remove if you start to sweat. You’ll be much better off wearing a very thin crew or quarter-zip shirt and adding additional thermal or wind-blocking layers on top of it if you start to feel a chill.

For example, you can exert a finer degree of control over your warmth level if you wear a lightweight baselayer top instead of a medium or heavy one and then add a second lightweight top over it if you start to feel a chill. There’s virtually no weight difference clothing-wise in this approach, but it gives you a much finer level of control over how warm you want to be when hiking in winter.

For the rest of this article, I’m going to focus winter layering with shirts and upper body insulation. For a detailed discussion about how to layer pants for winter hiking, see “Winter Pant Layering for Hikers that Sweat.” The same principles apply here. 

Perspiration is Bad

The problem with being too warm in winter is that it causes you to perspire. Perspiration is bad because it burns more calories, but that’s a hard concept for most people to understand and internalize. A more obvious outcome is that perspiration causes the air pockets in your clothing to clog up with liquid. This reduces the size of the air pockets in your clothing that trap warm air, reducing their ability to insulate you.

Some perspiration is inevitable, even when your body is at rest. Called insensible perspiration, you’re body emits about 400 ml of water per day through your skin. The Greeks were the first people to observe this fact thousands of years ago.

Layering

While you can’t completely stop perspiration, you can manage the degree that it degrades your clothing’s insulation value by wearing hydrophobic clothing that transports any water it absorbs away from your skin. This approach, commonly called layering, is best accomplished by wearing thin, highly porous clothing next to your skin. When layering, you want to preserve that wicking action through as many layers as possible. The goal is to move moisture from your skin to an outer layer where it can evaporate.

For example, I use three core layers in my winter hiking layering system:

  • A thin lightweight long sleeve jersey, usually synthetic.
  • A lightweight fleece hoody
  • A nylon windbreaker

That’s it, down to about 15 degrees. I can tell it’s working because the underarms of my wind shirt are damp and stinky at the end of the day. That means my perspiration is evaporating from the outermost layer.

Winter hikers often strip down to their baselayer when they’re working hard
Winter hikers often strip down to their baselayers when they’re working hard

The Next-to-Skin Layer

I’ve found that the most important garment in my layering stack is the foundational next-to-skin garment. Look for tops that you can see through when you hold them up to the light. I prefer synthetic long sleeve tops because they don’t absorb as much moisture and are very effective at wicking moisture up to my next layer. Wool can work too, especially wool garments that combine synthetic and wool yarns because they wick like synthetic tops but smell less due to their wool content.

Here are the next-to-skin tops that I use and that you might find useful to try.

But I can’t stress this enough. Keep that next-to-skin layer thin so that moisture can move quickly through it and up into your next layer. While it’s not intuitive, you’ll stay warmer if you stay cooler and perspire less during the course of the day.

See also:

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12 comments

  1. Great article Phil currently and am using an IOMerino light weight zip and love the piece. But, I am thinking about purchasing an Outdoor Vitals Dragonwool Hoodie. They are coming back in stock soon. Have a great New Year.

  2. I have two midweight, Patagonia half-zip capilene tops, one medium that is snug and the other is a size large which is “roomier”.
    In your opinion, which size/fit would best wick away perspiration?

  3. My all-time favorite is a Mammut PowerWool 1/4-zip baselayer, which has a very fine micro-grid on the skin side, but it’s really hard to find now, as they seem to have stopped making it. I’ve worn it hiking, biking, and on 20-hour intercontinental trips, and the PowerWool comes through looking good without any funk.

    Recently tried an Under Armour ColdGear compression shirt and found it horrible. Never felt warm and seemed to keep the moisture very close to the body, leaving me clammy and cold at the end of the ride.

    • I agree with this article. I use a Smartwool Men’s Merino 150 Base Layer 1/4 Zip for most winter hiking (snowshoeing) in Sangre de Christo mountains of Colorado. I find it wicks fairly well (maybe not as good a synthetic hybrid) and also keeps me warm when hiking up to high elevation. On the return I just add layers.

  4. I relate to this and use a thin base layer. I’ve reached the summit of a steep climb in 10 degrees with just a base layer with ice crystals growing out of my chest, I have a male friend who would be bare chested in the same conditions.

  5. Great article. I have also found that baggier base layers are warmer than tighter fitting ones of the same weight. They also breathe better, which helps sweat to dry and didn’t feel as sticky when you start to warm up. To prevent drafts when starting out or resting, the outer layers should seal at the waist and cuffs and a thin scarf or buff can prevent drafts at the neck. Regardless, the base is more versatile if it’s loose.

  6. Patagonia Merino Air (renamed as Patagonia Capilene Air) knit base layer is also very good for this.

  7. Been using the HH LIFA crews for years, they are truly a four season item for me. They’ll get used from temps 20’s to 60’s. Below 20 I use a thicker grid fleece top (Under Armour 2.0, which seems to be discontinued), and above 60’s it’s a synthetic short sleeve. Best thing about the HH is they are fairly inexpensive and often are on sale for $30.

  8. Thanks for this article Phillip. What’s your favorite Fleece hoody? You mentioned you wear it as your midlayer in the article.

    • I have an assortment of fleece hoodies, vests, and hoodless pullovers I rotate through in different weights (warmths), none of which are currently available for sale (they last forever). The ones I use the most are a Ragged Mountain Equipment Highland Hoody (no longer made) and the Montane Iridium Hoodie (no longer made). These are both mid-weight. If I were going to buy something new, I’d probably get this:

      https://www.amazon.com/North-Face-Glacier-Hoodie-Taupe/dp/B07MXLY25T

      It’s become increasingly difficult to find fleece that has a simple, basic, fuzzy exterior but it’s the best at wicking in my opinion. It’s also very inexpensive. If you’re hiking on a very cold day, you’ll see frost form on the outside of your sweater. That’s the moisture from your baselayer wicking through and freezing.

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