Cold weather activity poses unique risks to comfort and safety that other seasons typically don’t. One of the biggest risks threatens the regulation of warmth and wicking of moisture - both of which can have dangerous consequences beyond simple discomfort. This ‘base layer’ lays next to your skin, helping to maintain warm body temperatures while allowing moisture from perspiration to escape.
Base layers come in many shapes and forms. From sports bras to T-shirts, everybody has their go-to pick in any given situation. But thermal underwear is a must-have for anyone participating in winter activities like snowboarding, downhill skiing, cross-country skiing, or winter hiking due to its unique properties. There are a few considerations to keep in mind when choosing your thermal underwear to ensure the best purchase for your needs and planned activity.
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Weight
Base layers and thermal underwear come in different weights that are suited for a variety of different situations. Note that what seems logical (lighter weights working better for warmer scenarios) is fairly accurate.
Weight | Guidelines | Best for: |
Microweight | The lightest and thinnest of base layers; best suited for warmer (mild to cool) conditions or high-movement activities |
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Lightweight | Thin and designed with moisture management as priority |
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Midweight | Can be worn as a warm first layer or second layer; provides combination of insulation and comfort |
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Heavyweight | Known as ‘expedition weight’, these are the thickest and designed with insulation in mind. |
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The best way to choose the weight is to base it on your activity as well as whether or not you get cold easily. Layer with the understanding that you can remove layers should you get too warm. Remember that snug-fitting base layers will up the ante with insulation while looser-fitting layers allow for more air circulation and, thus, less insulating properties.
Material
Thermal underwear and base layers in general tend to be comprised of two main types of materials: synthetics (like polypropylene) or Merino wool. Both of these fabrics will help wick away moisture from the skin, reducing instances where sweat buildup causes discomfort. Similarly, these fabrics will dry much faster than, say, cotton counterparts and will help reduce the chances of dramatic changes in body temperature or regulatory properties.
Material | PROS | CONS | Best for: |
Synthetics (polyester blends, nylon, spandex, elastics) |
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Wool |
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Types
Once you’ve narrowed down the materials and weight of your thermal underwear that you’ll be needing, then it’s time to choose the type of base layer. Thermal underwear comes in many different shapes and forms, allowing users to purchase multiple layers with different coverages and fits for different situations.
Long Sleeve : These are generally used in colder conditions as a base layer but can also be paired as a second layer that covers a short-sleeve top as well.
Short Sleeve : While not regarded as ‘thermal underwear’ per se, a short sleeve base layer can be helpful for it’s cooling properties during warmer treks.
Long Leg : Snowboarding, skiing, alpine hiking, riding in cold weather are all examples of activities that need a long leg base layer which is intended for coverage and warmth in colder conditions.
Three Quarter Leg : Skiers and snowboarders sometimes prefer the three quarter leg bottoms which stay out of the boot, helping to eliminate discomfort.
One Piece : The ultimate in thermal underwear protection, a full suit covers a majority of your body - and some even come with a hood to keep warmth from escaping from your head. Opt for this during expedition-type activities.
