The best base layer for extreme cold weather is designed not necessarily to keep you warm but to create a second skin that keeps you dry from our own body perspiration. The best base layer for cold weather must be absorbent in the inside to wick away moisture from the body fast, as well as the ability to dry quickly to ensure sweat doesn’t linger too long against the body.
If you’ve got a trip coming up where you expect extreme cold weather and don’t even know where to start when it comes to buying a good quality women’s or men’s thermal base layer – then this is the perfect guide for you.
In this guide, I take you through everything you need to know to ensure you purchase the best thermal base layers for extreme cold weather. First up, I’ll take you through the various features you need to consider when looking for a good quality extreme cold weather base layer and then take a closer look at some of the top-rated options for both a women’s and men’s cold weather base layer.
This post may contain compensated links. Please refer to my disclaimer here for more information.
What is Base Layer Clothing? 
If you’re not familiar with super cold temperatures, you may not even be familiar with what a base layer is or what the purpose of it is – so let’s explain that first.
A base layer is a piece of clothing that is designed to be worn directly against your skin. Unlike standard underwear, the purpose of base layer clothing for cold weather is to wick away sweat from the body to avoid your body getting cold. It’s also designed to be fast-drying, to prevent that chill factor when moisture lingers against your body.
When traveling to destinations with extreme cold weather conditions, a good quality base layer is essential. Even more so if you plan on being active and the chances of your body sweating are high. While your body will feel warm while being active, once you stop, if your body is wet from sweat, you will quickly become cold, if not wearing a suitable base layer.
For extremely cold weather, you will also need a middle layer (to retain your body heat and protect you from the cold weather) and an outer layer (to shield you from the wind and rain).
My Pick for the Best Base Layer for Extreme Cold Weather: Smartwool Base Layers 
Don’t have time to read my entire men’s and women’s cold weather base layer clothing guide? I just love both the women’s and men’s base layers from Smartwool. They come in a great range of color options, and the 100% merino wool is super soft and great at locking in heat, but they won’t add unnecessary bulk as a first layer.
Click the below links to buy now or keep reading below to read my detailed review:
Womens: Smartwool Base Layer Top and Smartwool Base Layer Bottom
Mens: Smartwool Base Layer Top and Smartwool Base Layer Bottom
Comparison Chart for the Best Base Layer for Cold Weather 2020
Below I’ve provided a handy chart that details the various women and men’s winter base layer options reviewed in this guide. Use this table as a quick guide to see the products and their features side by side so you can determine if it’s the right option as a thermal base layer (women or men) for you.
| IMAGE | PRODUCT | Women/Men | Fabric | Weight | Price Guide | |
|---|---|---|---|---|---|---|
EDITOR’S CHOICE |
1. Smartwool 250 | Women | Merino | Mid Weight | $$ | Check Price |
RUNNER UP |
2. Arc’teryx Rho AR | Women | Polyester | Mid Weight | $$ | Check Price |
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3. Minus33 Expedition | Women | Merino | Heavy Weight | $$ | Check Price |
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4. Duofold | Women | Polyester | Heavy Weight | $ | Check Price |
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5. MERIWOOL | Women | Merino | Mid Weight | $ | Check Price |
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6. Smartwool | Men | Merino | Mid Weight | $$ | Check Price |
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7. WoolX Glacier | Men | Merino | Heavy Weight | $$ | Check Price |
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8. Minus33 Expedition | Men | Merino | Heavy Weight | $$ | Check Price |
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9. Arc’teryx Rho AR | Men | Polyester | Mid Weight | $$ | Check Price |
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10. Meriwool | Men | Merino | Mid Weight | $ | Check Price |
Things to Consider when Purchasing the Best Thermal Base Layers
To purchase the warmest base layer for extreme cold weather, that’s perfect for you, be sure to consider the following factors:
1. Fabric
When it comes to the warmest base layer for cold weather, the most crucial factor to consider is the fabric. Unlike standard underwear, good quality base layers are made from either silk, merino, wool, or synthetics such as polyester or nylon. There are subtle differences in each of the fabrics, and below I have briefly covered the advantages and disadvantages of each.
Merino
Merino baselayers are considered by many (including me) to be the best type of base layer. Merino base layers are great for almost all kinds of weather conditions, great at quickly wicking away moisture and are naturally odor-resistant.
Characteristics of merino include:
- Great at wicking away moisture from the skin, although it does take longer to dry than synthetic fabrics.
- Great at being naturally odor resistant – you can wear merino base layers multiple times before it needs to be laundered.
- Soft and feels great against the skin.
- Merino is relatively expensive compared to other fabrics.
Synthetics
Next to merino, synthetics (such as rayon, nylon, polypropylene, polyester, spandex, and other synthetic blends) are also a popular choice for base layers.
Characteristics of synthetics include:
- Excellent at wicking away moisture from the skin and quick drying.
- Feels nice and soft against the skin.
- Synthetics are not as great as merino in terms of odor-resistant and can’t be worn over and over again without being laundered.
Silk
Base layers made from silk are incredibly soft and are a good option for people not likely to do anything too active during their travels. However, these days, silk isn’t that common for base layers.
Characteristics of silk include:
- Works well at wicking moisture away from your body, provided you’re not engaged in anything too active. For more active travelers, silk is not a great option, and other fabrics work better at wicking away sweat from the body.
- Lightweight – easily fits under your outer layers without adding bulk to your appearance.
- Silk is not naturally odor resistant, so not recommended for people likely to sweat.
Cotton
Do not buy base layers made from cotton! While everyday underwear is made from cotton, it is not designed to wick away sweat and retains dampness which means it will do nothing to keep you warm in cold weather.
2. Weight
Another factor to consider when purchasing base layers is the weight of the garment. Base layers tend to be classed as lightweight, midweight and heavyweight. For the warmest base layer clothing, a mid or heavyweight is recommended.
Below I’ve provided a brief overview of the different weights and when they are best used:
- Lightweight: For cool to moderately cold conditions designed to be loose and have good air circulation.
- Midweight: For moderately cold to cold conditions where warmth is required and designed to be worn as part of a clothing layering system.
- Heavyweight: For use in extremes of wind and cold weather in which warmth is essential as part of a clothing layering system.
Just remember, the purpose of the base layer is moisture management and not to provide warmth. While heavier base layers can add some warmth, it’s the insulating middle layer that’s designed to keep you toasty.
3. Fit
For a base layer to do its job in freezing weather, it needs to have a snug fit – remember it’s designed to be a second skin. By sitting directly against your skin, the garment can wick away sweat effectively.
You should also ensure your base layer has elastic cuffs to ensure no body heat escapes.
The Best Base Layer Clothing for Cold Weather
Below I’ve reviewed some of the top-rated options currently on the market for the best women’s base layers and the best men’s base layers for cold weather.
Best Women’s Cold Weather Base Layer Clothing
1. Smartwool Women’s Base Layer 
Want a base layer that is super warm, comfortable and still looks great and comes in a range of options? Take a good look at the Smartwool women’s base layer top and bottom!
This base layer set is made from 250gm 100% merino wool that feels soft and luxurious against your skin. The material is an interlock knit which gives it extra breathability and thermoregulation, and the tag-free garments mean no itchy labels.
The top in this set comes in an impressive 12 color choices, so there is something to suit every style, and the shoulder seams are offset to the front to avoid rubbing from backpack straps. The ankle-length pants come in a choice of 5 colors and have a wide comfortable waistband.
If you want the chance to mix and match your colors or intend on wearing these as stand-alone garments indoors as well as out as a base layer, the Smartwool thermals let you look stylish and stay warm.
Click the below links to read more reviews and to check the current price:
Women’s Smartwool Base Layer Top 
Women’s Smartwool Base Layer Bottom
2. Arc’teryx Rho AR Base Layer 
This base layer top and base layer bottom from Arc’teryx provide maximum coverage and heat retention for anyone who wants serious warmth in icy conditions.
These garments are made from a 90% polyester, 10% elastane material with Polartec power stretch properties, so they are fitted but don’t restrict movement. The synthetic fleece material will keep you really warm and has excellent moisture-wicking capabilities. This set also has flatlock seams for increased comfort. 
The top in this set comes in a choice of five colors and has a mid-chest to collar zip which allows you to lock in extra warmth but then vent air efficiently. The top also has an added pocket on the sleeve is a nice touch. The pants come in a choice of two colors and have a handy thigh security pocket in the thigh.
If you want something super warm and only plan on doing moderate activity, these thermals will keep you cozy warm without overheating.
Click the below links to read more reviews and to check the current price:
Women’s Arc’teryx Rho AR Base Layer Top
Women’s Arc’teryx Rho AR Base Layer Bottoms
3. Minus33 Merino Wool Women’s Expedition Base Layer 
If you want a pair of thermals from a company well known for delivering high-quality products for years, Minus33 are the way to go. Check out these Minus33 merino wool base layer top and bottoms.
These base layers are made from 100% 18.5 Micron Merino Wool that is 400 g/m2, so they really keep you warm in the freezing weather. The interlock knit construction, and flatlock seams add extra stretch and comfort to provide a high-quality set. They even have a UPF Rating 50+ and come in a huge range of sizes from XS to 3XL to make sure everyone can find a size that fits perfectly. 
Both the top and pants are completely tagless to eliminate the itching and scratching associated with a traditional tag, and they both feature stretchable rib knit cuffs, which help to keep sleeves in place for easy layering and allow for ease of movement.
If you’re after a high-quality merino base layer for icy weather conditions, this set from Minus33 is well worth considering.
Click the below links to read more reviews and to check the current price:
Women’s Minus33 Base Layer Top
Women’s Minus33 Base Layer Bottoms
4. Duofold Women’s Heavyweight Base Layer Set
Those who want a heavyweight baselayer but don’t have the budget for 100% merino wool, will like this base layer top and bottom set from Duofold that is high quality but still affordable.
Made from a 96% polyester and 4% spandex mix double-layer ring-spun fabric, these base layers wick away moisture effectively. This two-layer fabric knits together tightly to trap body heat and create a thermal barrier against freezing weather. The flatlock seams prevent chafing, and the tag-free labeling means no more scratchy irritating labels.
This baselayer set has a top with a crew neck and a contoured hem to prevent riding and make sure there is full coverage, even during vigorous activity. The ankle-length pants provide maximum coverage, and the drawstring waist allows for extra comfort and ease of fitting
If you want a heavyweight thermal base layer that won’t break the bank, take a look at these Duofold thermals for a set that is great at locking in body warmth.
Click the below links to read more reviews and to check the current price:
Women’s Woolx Base Layer Bottoms
5. Meriwool Women’s Baselayer
If you want a high-quality merino wool base layer and don’t mind spending a little extra to get the best, this merino wool top and bottoms from Meriwool are well worth considering.
This set is a heavyweight and extremely warm base layer due to the 100% superfine 18.5 micron, 400gsm merino wool that feels soft and comfortable against your skin. They are quick-drying, efficient at wicking moisture away from the body and have a UPF rating 50+. 
The top has a crew neck and the fitted cuffs help retain as much body heat as possible. The bottoms have an excellent stretch to allow for freedom of movement and are completely opaque and comfortable enough that they could easily double as yoga pants.
If you want a high-quality base layer that provides heaps of warmth with a versatile pant that can be worn out hiking or even indoors for yoga, definitely opt for this Meriwool set.
Click the below links to read more reviews and to check the current price:
Women’s Meriwool Baselayer Top
Women’s Meriwool Baselayer Bottoms
Best Mens Base Layers for Cold Weather
6. Smartwool Men’s Base Layer Merino 250
Want a base layer top and bottom that is super warm, comfortable and still looks great and comes in a range of options? Take a good look at the Smartwool men’s base layer!
This base layer set is 100% merino wool that is 250gm and feels soft and luxurious against your skin. The interlock knit material gives extra breathability and makes these thermals great at retaining body heat, while the tagless labeling means no itchy labels to deal with. 
The top comes with a whopping 10 color choices, so you’re sure to find something to suit your style. You’ll also appreciate how the shoulder seams are offset to the front to avoid rubbing from backpack straps. The ankle-length pants come in a choice of 7 colors and come with flatlock seams for extra comfort and have an open fly design.
If you plan on wearing these not only as a base layer but as a single layer around the house the Smartwool thermals give you the chance to mix and match your colors to look stylish and stay warm.
Click the below links to read more reviews and to check the current price:
Men’s Smartwool Base Layer Top
Men’s Smartwool Base Layer Bottoms
7. Minus33 Merino Wool Men’s Expedition Base Layer
If you are looking for a high-quality base layer top and bottom from a company that has built trust by using the best materials and using top quality design, Minus33 could be the way to go.
This set is made from 100% 18.5 Micron Merino Wool that is 400 g/m2, making them incredibly warm in the freezing temperatures. The interlock knit material and flatlock seams provide extra comfort and range of movement. They even have a UPF Rating 50+, and the size range is impressive with XS to 3XL so you should easily find a pair that fits perfectly. 
The top and pants are both completely tag free so no itching and scratching which is usually associated with traditional tags. They both also have stretchable rib knit cuffs to the ankles and wrists, to keep sleeves and legs in place which makes for easy layering. The pants also feature an open design fly for easy toilet breaks.
If you want a high-quality merino wool base layer, this set from Minus33 is well worth considering.
Click the below links to read more reviews and to check the current price:
Men’s Minus33 Base Layer Bottoms
8. Arc’teryx Rho AR Base Layer
This base layer top and bottom set from Arc’teryx provides maximum coverage and heat retention for anyone wanting high warmth in super cold conditions.
This set is made from a 90% polyester, 10% elastane mix synthetic fleece material with Polartec power stretch properties, making them fitted and efficient but still with enough stretch that they don’t restrict movement. This set also has flatlock seams for increased comfort against the skin. 
The top has a chest to collar zip, which locks in extra warmth and, when opened, vents air efficiently to cool down fast. It also comes with a handy security chest pocket and comes in a choice of five colors. The pants have a wide waistband for comfort, a thigh pocket for valuables and come in a choice of two colors.
If you want something super warm for moderate activity, the Arc’teryx Rho AR base layer will keep you warm without overheating.
Click the below links to read more reviews and to check the current price:
Men’s Arc’teryx Base Layer Top
Men’s Arc’teryx Base Layer Bottoms
9. WoolX Glacier Merino Wool Base Layer 
These heavy weight, high quality men’s base layers are perfect for anyone wanting warmth in icy conditions.
This top and bottom base layer are made from 100% Australian sourced Merino Wool which is 18.5 Micron and 400g/m, so you know you’re getting a high-quality set that will keep you warm in freezing weather. The pants are “heavyweight” but don’t let that label fool you as they feel light on and won’t add unnecessary bulk to your clothing. 
The crew neck comes in a choice of 5 colors, and the long hem won’t ride up during heavy activity. The sleeves even have a wide 3-inch cuff with hidden thumbholes to make layering easy and add extra warmth to the hands when needed. The pants include flatlock seams to stop chafing, easy front access fly for when nature calls, a non-slip waistband, and wide bottom cuffs that won’t ride up.
If you plan on being very active in your base layer, you can’t get much better than these Woolx Glacier thermals.
Click the below links to read more reviews and to check the current price:
Men’s Woolx Glacier Base Layer Top
Men’s Woolx Glacier Base Layer Bottoms
10. Meriwool Midweight Merino Base Layer
These high quality base layers from Meriwool are a great choice for anyone who wants a great quality top and bottom base layer, as well as something that will stand up to regular use without too much wear and tear.
These are heavyweight base layers, designed to withstand the extreme cold weather and keep you toasty and warm thanks to the 100% superfine 18.5 micron, 400gsm merino wool. These Meriwool base layers feel really soft against your skin, are quick-drying, super-efficient at wicking moisture away from your body, and even have a UPF rating 50+. Both the top and the pants come in a choice of 8 different colors. 
The top is crew neck style and has a slightly longer hem so it won’t ride up during heavy activity, while the bottoms stretch to allow freedom of movement and feature an open double-layer fly to allow for easy toilet breaks.
If you want high quality, a wide choice of colors and heaps of warmth definitely consider these base layers from Meriwool.
Click the below links to read more reviews and to check the current price:
Men’s Meriwool Baselayer Bottoms
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