The best thermal underwear for extreme cold weather is designed not necessarily to keep you warm but to create a second skin that keeps you dry from your own body sweat. When it comes to extreme cold weather thermals for women and men, it’s essential that they are absorbent on the inside to wick away moisture from the body quickly, as well as being able to dry rapidly, to ensure sweat doesn’t linger too long against the body.
If you’re headed to a super cold destination and in the market for the best thermal underwear for women or men, then this is the perfect guide for you. In this guide, I take you through everything you need to know to purchase the warmest thermal underwear for women and men. First up, I’ll take you through the various features you need to consider when looking for good quality extreme cold thermal underwear and then I’ll take a closer look at some of the top-rated options for both women and men’s thermal underwear.
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What is Thermal Underwear? 
If you’ve never ventured into super cold temperatures, then you probably have never even worn thermals before. So, before we get into the cold weather thermal underwear reviews, let’s first explain a little bit more about the purpose of thermals.
Thermals (or long johns as they are also called) are a combination of thin long pants and thin tops with long sleeves designed to be worn directly against your skin with other layers of clothing on top. Together the layers of clothing keep you warm in cold climates.
Unlike standard underwear, the purpose of thermals is to wick away sweat from the body to avoid your body getting cold. Thermals are 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, good quality thermals are 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 when moving about, as soon as you stop and rest if your body is wet from sweat, you will quickly become cold if you’re not wearing thermals.
For icy 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 Thermal Underwear for Extreme Cold Weather:
Women: LAPASA Thermal Underwear Set
Men: Icebreaker 200 Oasis Top and Bottom Thermals
Don’t have time to read my entire best thermal underwear for men and women guide? For women, I just love the thermal set from LAPASA and for men I love the Icebreaker Oasis Top and Bottom. Both these sets of thermals are made with high quality 100% merino wool and come with an affordable price point for everyone.
Click the links below to purchase or keep reading below to read my detailed extreme thermal underwear reviews.
- Women’s LAPASA Merino Wool Thermal Underwear Set
- Men’s Icebreaker Oasis 200 Thermal Top and Thermal Bottom
Comparison Chart for the Best Thermal Underwear for Men and Women 2020
Below I’ve provided a handy chart, which details the various womens and mens extreme underwear 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 extreme cold weather thermal underwear for you.
| IMAGE | PRODUCT | Women/Men | Fabric | Weight | Price Guide | |
|---|---|---|---|---|---|---|
 |
1. ColdPruf Quest | Women | Polyester | Midweight | $$ | Check Price |
 |
2. LAPASA | Women | Merino | Midweight | $$ | Check Price |
 |
3. Duofold | Women | Polyester | Heavyweight | $$ | Check Price |
 |
4. Mancyfit | Women | Polyester | Midweight | $$ | Check Price |
 |
5. Meriwool | Women | Merino | Heavyweight | $$$ | Check Price |
 |
6. LAPASA M24 | Men | Polyester | Heavyweight | $$ | Check Price |
 |
7. ColdPruf Quest | Men | Polyester | Midweight | $$ | Check Price |
 |
8. David Archy Set | Men | Acrylic + Rayon | Heavyweight | $$ | Check Price |
 |
9. Icebreaker Oasis | Men | Merino | Midweight | $$$ | Check Price |
 |
10. Woolx Glacier | Men | Merino | Heavyweight | $$$$ | Check Price |
Things to Consider when Purchasing the Best Thermal Underwear for Women and Men
To purchase the warmest thermal underwear for extreme cold weather, be sure to consider the following factors:
1. Fabric
When it comes to thermals, the essential factor to consider is the fabric. Unlike standard underwear, women and men’s thermal underwear for extreme cold weather are usually made from either 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) as the best type of fabric for extreme cold weather long johns. Merino base layers are great for almost all kinds of weather conditions; they’re 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 thermals 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, synthetic (such as rayon, nylon, polypropylene, polyester, spandex, and other synthetic blends) is also a popular choice for extreme cold weather long underwear.
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 resistance and can’t be worn over and over again without being laundered.
Silk
While you can get thermals made with silk, generally they are not as effective as merino or synthetic thermals in frigid weather. Thermals made from silk are however incredibly soft and can be an option for people not likely to do anything too active during their travels.
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 a lot.
Cotton
When it comes to freezing weather, do not buy thermals made from cotton! While everyday underwear is made from cotton, cotton is not designed to wick away sweat and retains dampness, which means it will do nothing to keep you warm in super cold temperatures.
2. Weight
Another factor to consider when purchasing thermals is the weight of the underwear. Thermals tend to be classed as lightweight, midweight and heavyweight. For the best extreme cold long underwear, 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 thermals is moisture management and not to provide warmth. While heavier thermals can add some warmth, it’s the insulating middle layer that’s designed to keep you toasty and warm.
3. Fit
Thermals should have a snug fit and feel like a second skin. By sitting directly against your skin, this allows the thermals to wick away sweat effectively. Thermals should also have elastic cuffs to ensure nobody heat escapes.
The Best Extreme Cold Weather Thermals for Women and Men 2020
Below I’ve reviewed some of the top-rated women and men’s thermals for cold weather currently on the market.
The Best Thermal Underwear for Women
1. ColdPruf Women’s Quest Performance Thermals 
These ColdPruf women’s midweight thermals are designed with women in mind. The ColdPruf top and ColdPruf bottom are form-fitting in all the right places to ensure moisture is wicked away efficiently and suitable for all levels of activity in extreme cold.
This range is made from an 85% polyester, 15% spandex mix material, formulated with Silvadur Intelligent Freshness to minimize odor-causing bacteria and resist smells. This set also features tagless labeling and flat seams to ensure extra comfort.
The top features raglan sleeves with elasticized wrists and thumbhole cuffs to retain body heat and make layering comfortable and the drop tail ensures a full coverage, even during heavy activity. The bottom has a comfort waistband and front and back rise to maintain coverage at all times and the paneled legs allow for unrestricted movement and continual comfort.
These ColdPruf Performance thermals would suit anyone planning to be active in the extreme cold and needing a reliable set of extreme cold weather underwear that does not restrict movement or become uncomfortable after long periods of wear.
Click the link below to read more reviews and to check the current price:
ColdPruf Quest Performance Thermal Top 
ColdPruf Quest Performance Thermal Bottoms
2. LAPASA Women’s Merino Wool Thermal Underwear Set 
If you want a 100% Merino wool underwear set without the hefty price tag, then definitely consider this top and bottom combo from LAPASA.
This set is made from a high quality 100% 200gm, 18.5 microns merino wool which is not only comfortable but super soft against your skin and the rib knit gives a 4-way stretch that fits well. It also gives a really light feel and won’t bulk you down while still providing that important midweight moisture-wicking protection for outdoor activity.
The material of the hems and binding on the neckline is the same merino wool to improve stretch and heat retention and allow for a greater range of movement. The four needle, six thread stitching also makes for a really durable garment that will last you some time and the easy rip tag means no annoying scratchy labels.
These 100% merino wool thermals are perfect for anyone who wants the luxury of top quality material but with an affordable price tag.
Click here to read more reviews and to check the current price for the LAPASA Thermal Set
3. Duofold Women’s Heavyweight Double Layer Thermals 
If you’re looking for heavyweight thermals but don’t have the budget to stretch to 100% merino wool, this Duofold top and Duofold bottom would be a great compromise.
This thermal set is made from a 96% polyester, 4% spandex mix double-layer ring-spun fabric, which wicks away moisture efficiently. The two-layer fabric knits together, trapping body heat and creating a thermal barrier against the cold. The flatlock seams mean no chaffing and the tagless labeling means no irritation from annoying labels.
The top has a crew neckline and features a contoured hem to ensure proper waist coverage during heavy activity. The pants are ankle length to provide maximum coverage and have a drawstring waist for extra comfort.
If you need a pair of heavyweight thermal undergarments but don’t want to break the bank, take a look at these Duofold thermals for a pair that are comfortable and great at locking in body warmth.
Click the link below to read more reviews and to check the current price:
Duofold Double Layer Thermal Top
Duofold Double Layer Thermal Bottom
4. Mancyfit Fleece Lined Long John Set
If you just want a cheap set of women’s thermals that you can still rely on to keep you warm and go the distance, this set from Mancyfit is about as budget-friendly as they come!
This midweight option is made from a 95% polyester and 5% spandex mix material with 4-way stretch that is soft, comfortable and efficient at wicking away moisture. The inner layer is brushed and creates warmth, whereas the outer layer is smooth polyester making it easy to layer garments without them bunching up.
The top is a casual crew neck style, and the pants are full ankle length for maximum coverage. This set comes in a choice of three colors black, navy or white.
Anyone looking for a super affordable pair of cold weather thermals that let them stay active in the freezing temperatures would be happy with this budget option from Mancyfit.
Click here to read more reviews and to check the current price for the Mancyfit Fleece Thermal Set
5. Meriwool Heavyweight Thermals
If you are looking for some high-quality merino wool thermals and don’t mind spending a little extra to get a really great set, this Meriwool thermal top and Meriwoold thermal bottoms are exactly what you’ve been looking for.
These thermals are heavyweight and extremely warm thanks to the 100% superfine 18.5 micron, 400gsm merino wool, which is soft and comfortable against your skin. These garments are quick-drying, efficient at wicking moisture away from your body and have a UPF rating 50+. 
The top is a crew neck style and has fitted wrist sections to retain as much body heat as possible. The bottoms stretch to allow freedom of movement and are opaque and comfortable enough that they could easily double as yoga pants.
If you want high quality and heaps of warmth definitely opt for these thermals from Meriwool.
Click the link below to read more reviews and to check the current price:
Meriwool Heavyweight Thermal Top
Meriwool Heavyweight Thermal Bottom
The Best Men’s Thermal Underwear
6. LAPASA M24 Men’s Heavyweight Thermal Underwear Set 
If you are looking for a set of heavyweight cold weather underwear for men that is affordably priced, consider the LAPASA M24 set.
These heavyweight thermals are made from a 260g double layer material to trap warmth. The outer layer is a 95% polyester, 5% spandex mix. The inner layer is fleece lined, designed to be soft and comfortable against your skin and is excellent at wicking away moisture.
The stretch in the fabric gives great freedom of movement, and the crew neck top is casual enough to still look good when you head inside and remove top layers. This thermal underwear set also features an easy rip label, so no itchy tags and an open fly double layer design to make toilet breaks that much easier.
This LAPASA M24 set really ticks all the boxes – affordable, warm, comfortable and looks good.
Click here to read more reviews and to check the current price.
7. ColdPruf Men’s Quest Performance Thermals
This ColdPruf men’s midweight thermal top and thermal bottom set are great at wicking away moisture efficiently and have some extra little design features that make them great value.
These thermals are made from an 85% polyester, 15% spandex mix material, created with Silvadur Intelligent Freshness, which minimizes odors causing bacteria. This set features tagless labeling, to avoid itchy labels and flat seams for extra comfort.
The top has elastic thumbhole loops in the sleeves to make layering easier, and the drop tail ensures full coverage, even during heavy activity. The mock turtleneck design gives maximum coverage and heat retention. The bottom layer has a comfortable, non-itch waistband and front and back rise to maintain better coverage.
These ColdPruf Performance thermals would be a great choice for anyone planning to be active in the extreme cold and needing a reliable set of comfortable thermals.
Click the link below to read more reviews and to check the current price:
ColdPruf Quest Performance Thermal Top
ColdPruf Quest Performance Thermal Bottom
8. David Archy Ultra Soft Winter Warm Thermal Set
If comfort and feel are at the top of your list of essential features, these David Archy thermals are sure to impress with their ultra-soft, double fleece material.
This thermal set is made from a double layer fleece-like material, made from 66% rayon, 26% acrylic and 8% spandex and customers rave about how soft it feels against their skin. This is a 300g/m2 heavyweight set, intended to keep you warm in the coldest of environments and they even come in a choice of three colors.
Both the top and the pants have double-layered panels on the elbows and knees to protect these high use areas from wear. The top has a rounded crew neck design and elasticated cuffs for extra heat retention. The pants with this set also come with a functional open fly making it easy to go when nature calls.
The best thing about this thermal set really is the super soft material, but they also come at a great price point and with high quality manufacturing.
Click here to read more reviews and to check the current price.
9. Icebreaker Merino 200 Oasis Thermals 
If Merino wool is an absolute must for you, check out this thermal top and thermal bottom set from Icebreaker, who is known for making high quality Merino products.
These garments are made from 100% 200gsm merino wool so they are warm but only medium weight and the slim body fit design ensures maximum body heat is retained. Flat seams in both garments do an excellent job of preventing chafing. 
The top with this set comes in a choice of 4 different colors; black, stripe, grey or navy and has a carefully offset shoulder seam to prevent backpack straps from rubbing. The pants have a comfortable elastic waistband and a gusset in the crotch for comfort and ease of movement.
If you want Merino wool and high quality, Icebreaker Merino 200 thermals are certainly the way to go.
Click the link below to read more reviews and to check the current price:
Icebreaker Merino 200 Oasis Thermal Top
Icebreaker Merino 200 Oasis Thermal Bottoms
10. Woolx Glacier Men’s Merino Thermals
These men’s Woolx Glacier thermal tops and thermal bottoms would suit anyone looking for a heavyweight and high quality set to keep them super warm in icy conditions.
The 100% Australian Merino Wool is 18.5 Micron and 400g/m, so you know it’s high quality and will keep you warm in freezing weather. Despite it’s a “heavyweight” label and high-quality material these thermals feel light on and won’t add unnecessary bulk to your clothing. 
The top in this set comes in a choice of 5 different colors and has a long hem so it won’t ride up if you are very active. The sleeves also have wide 3 inch cuffs with thumbholes making layering easy as well as adding extra warmth for the hands if needed. The pants feature a no-roll waistband, flatlock seams to prevent chafing, a front easy access fly and wide bottom cuffs that won’t ride up.
If you want something high quality for an active lifestyle, you can’t get much better than these Woolx Glacier thermals.
Click the link below to read more reviews and to check the current price:
Woolx Glacier Merino Thermal Top
WoolxGlacier Merino Thermal Bottom
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