Extreme Cold Weather Thermals

In this article, we will take you through the best thermal options you can pick from. We have examined the features and advantages of all of them, so you can easily choose the best one for your needs.

Let’s dive right in!

Best Thermal Underwear for Extreme Cold

The convenient table below will give you a quick preview of our top thermal underwear picks for extremely cold conditions.

It will serve as a quick guide so you can analyze the best options along with their features, and ultimately determine the best option for you.

Overview of Thermal Underwear for Men

Product NameProduct ImagePriceMaterialOur Rating
Icebreaker Merino Men$$Merino Wool 200g/m25
David Archy Men$$66% Rayon, 26% Acrylic, 8% Spandex4.5
ColdPruf Men$$85% Polyester/15% Spandex4.5
LAPASA Men$$Heavyweight: 95% polyester, 5% spandex; Ultra Heavyweight: 44% polyester, 52% cotton, 4% spandex(Outer Material);95% polyester, 5 spandex(Inner Material).4
WoolX Glacier$$$100% Australian Merino Wool - 18.5 Micron - 400g/m²4

Overview of Thermal Underwear for Women

Product NameProduct ImagePriceMaterialOut Rating
MERIWOOL Women $$100% Merino Wool - 18.5 Micron - 400g/m5
Smartwool Women’s Base Layer Top $$Merino Wool 250g/m25
Icebreaker Merino Women's 260 Tech $$$100% Merino Wool 260g/m24.5
ColdPruf Women $85% Polyester/15% Spandex4.5
Duofold Women $96% Polyester/4% Spandex Bi-ply4

Best Thermal Underwear For Men

Icebreaker Merino 200 Oasis Thermals

The Icebreaker Merino 200 Oasis Thermals are crafted from 100% 200g/m2 wool. They come with slim body fit, medium weight that provides optimal heat regulation. Also, these thermals don’t chafe because of flat seams in both garments.

The top of these thermals comes in four different colors which include navy, grey, stripe, and black. It comes with a delicately offset shoulder seam in order to prevent backpack straps from chaffing. Additionally, the pants come with a gusset in the crotch for better movement and comfort. The pants are also incorporated with an elastic waistband for additional comfort.

Icebreaker is famous for crafting high-quality Merino products. So, if you’re looking to get Merino wool, then the Icebreaker Merino 200 Oasis Thermals are perfect for you.

David Archy Ultra Soft Winter Warm Thermal Set

If you prefer comfort and feel than any other, then the David Archy Ultra Soft Winter Warm Thermal Set is perfect for you as it comes with ultra-soft, double fleece material.

These very good thermals are crafted from base layer fleece-like material. It is made from 8% spandex, 26% acrylic, 66% rayon. Users love how soft these thermals feel against their skin. This thermal set is intended to maintain your body core temperature in extreme freezing conditions because of its 300g/m2 material. Additionally, they come in three different colors.

Both the pants and the top come with double-layered panels on the knees and elbows in order to protect these parts from wear and tear because of excessive use. The pants are incorporated with a convenient open fly that will make it convenient when nature calls. On the other hand, the upper comes with elasticated cuffs and rounded crew neck design for additional heat retention.

Aside from high-quality manufacturing and reasonable price range, one of the best things about these thermals is its super soft material.

ColdPruf Men's Quest Performance Thermals

The ColdPruf Men’s Quest Performance Thermals are highly effective in terms of wicking away moisture. These excellent thermals are crafted with Silvadur Intelligent Freshness in order to reduce bacteria that cause odors. Moreover, they are crafted from 15% spandex and 85% mixed materials. These thermals feature flat seams for additional comfort, and tagless labeling to get rid of itchy labels.

The pants come with a front and back rise to maintain better coverage. It also features a comfortable, non-itch waistband. Also, the top comes with a drop tail that ensures full coverage even during intense activities. The upper also features elastic thumbhole loops in the sleeves in order to make layering more convenient.

If you’re planning to be very active in extremely cold conditions and want reliable and comfortable thermals, then the ColdPruf Men’s Quest Performance Thermals would be a great pick.

LAPASA M24 Men's Heavyweight Thermal Set

The LAPASA M24 Men’s Heavyweight Thermal Underwear is in the top 3 of the most reasonably-priced and heavyweight thermals in this list. This set is made from 260g/m2 double-layer material to retain heat. These thermals’ base layer is fleece-lined and made to be comfortable and soft against your skin, which is also great at wicking away moisture. On the other hand, the outer layer is 5% spandex and 95% polyester mix.

The crew neck top has a casual feel to still look good even if you remove upper layers. Additionally, the stretch in the material provides excellent movement coverage.

Furthermore, these thermals also come with an open fly double layer design to make the call of nature easier. This set also comes with an easy rip label, so no itchy tags for you.

Overall, the LAPASA M24 Men’s Heavyweight Thermal Underwear Set is comfortable, warm, reasonably-priced, and looks good.

Woolx Glacier Men's Thermals

If you’re searching for a high-quality and heavyweight set to keep you warm in freezing conditions, then the Woolx Glacier Men’s Thermal Underwear would suit you perfectly.

Keeping you warm with this high-quality thermal is easy because it is incorporated with 100% Australian Merino Wool that comes with 400 gram/m2 and 18.5 micron. Even though it is labeled as “heavyweight”, the Woolx Glacier Men’s Thermals will still feel light on.

It comes with a long hem so you don’t need to worry about it even if you’re so active. Moreover, it comes in five colors so you can have more choices. Also, layering is easy with these thermal clothes because the sleeves come with wide three-inch cuffs incorporated with thumbholes.

Furthermore, the pants feature wide bottom cuffs that won’t ride up. It also comes with a front easy-to-access fly, flatlock seams to prevent chafing, and lastly a no-roll waistband. If you have a very active lifestyle, then the Woolx Glacier Men’s Merino Thermals won’t let you down.

Best Thermal Underwear For Women

Meriwool Heavyweight Thermals

Do you prefer Merino wool over other types of fabric? Are you willing to spend a little more for a set of high-quality layers? Then the Meriwool Heavyweight Thermals Set is perfect for your needs.

This set is extremely warm and heavyweight because it is incorporated with 100% 400g/ms merino wool and superfine 18.5 micron, which is comfortable and soft against your skin. These thermals have a UPF rating 50+ and are quick-drying and very effective at wicking moisture away from your body.

The bottoms stretch to provide better movement range. Also, they are comfortable enough if you want to double them as yoga pants. Additionally, the top comes with fitted wrist sections to retain your optimal body core temperature. Also, the upper is a crew neck style.

All in all, Meriwool thermals are perfect for you if you want heaps of warmth.

Smartwool Women's Base Layer Top - Merino 250 Wool Pattern Active Crew

The Smartwool Women’s Base Layer Top is warm, soft, and stretchy. Its sleeves are long enough. It is perfect against the chill of a winter hike. Even if you’re very active, this base layer top will still provide you great comfortability because of its targeted insulation and ventilation.

Also, since it is made from Merino 250, it greatly helps in maintaining your body core temperature. It also prevents odor-causing bacteria and effectively wicks away moisture while not compromising its breathability. But take note, since it is made from Merino 250, it should be machine washed in warm water on a gentle cycle and tumble dried on low.

Lastly, it has excellent durability because of its flatlock seam construction that is specially crafted to significantly reduce chafing. Also, this base layer top is designed with an interlock knit for improved odor-resistance, thermoregulation, breathability, and added comfort.

Duofold Women's Heavyweight Double Layer Long John Set

The Duofold Women’s Heavyweight Double Layer Thermals would suit you perfectly if you’re searching for heavyweight thermals but don’t really have the budget to afford 100% wool.

These thermals are crafted from 4% spandex and 96% polyester mix double-layer ring-spun material, which effectively wicks away moisture. This thermal set is efficient at making a thermal barrier against cold temperature and retaining your optimal body heat. Moreover, it features tagless labeling for less irritation and flatlock seams to prevent chafing.

The pants feature a drawstring waist for added comfort and are ankle length to give an optimal range of motion for the user. Also, the top comes with a contoured hem to guarantee the right waist coverage during intense activities. The top also features a crew neckline.

If you don’t want to spend that much but want a pair of heavyweight thermals, then make sure to consider the Duofold Women’s Heavyweight Double Layer Thermals.

Icebreaker Merino Women's 260 Tech Long Sleeve Crewe Base-Layer-Tops

This Merino base-layer tops from Icebreaker is a top contender as it features a very warm design with a huge range of thermoregulation.

It offers excellent comfortability and incredible warmth because it is packed with 100% Merino wool 260g/m2. Aside from great thermoregulation, this base-layer top also gives you exceptional breathability while hiking uphill and sufficient warmth while skiing down.

Its fabric material effectively wicks away moisture to make you comfortable even during intense activities. On the flip side, layering takes a little bit of effort and it is not that durable. But still, this midweight thermal is ideal to wear as a layer or even on its own.

Overall, this base-layer top is a good choice because of its great range of thermoregulation and ample warmth that it provides.

ColdPruf Women's Quest Performance Long John Set

The ColdPruf Women’s Quest Performance Thermals are perfect for all levels of activity in extremely cold conditions. This set is form-fitting in all the appropriate areas to guarantee that moisture is wicked away effectively.

Aside from being crafted from 15% spandex and 85% polyester material, these thermals are also incorporated with Silvadur Intelligent Freshness in order to significantly reduce odor-causing bacteria. For additional comfort, these thermals also feature flat seams and tagless labeling.

The top of this set has Raglan sleeves that feature thumbhole cuffs and elasticized wrists to make layering comfortable and effectively maintain your body core temperature. Additionally, the top’s drop tail guarantees a good range of motion even during intense activities. On the other hand, the bottom features a comfortable waistband and front and back rise to maintain coverage consistently. Moreover, the paneled legs enable continual comfort because of unrestricted movements.

Overall, the ColdPruf Women’s Quest Performance Thermals is perfect for you if you want a reliable set of thermals and if you’re planning to be very active in an extremely cold environment.


How is a base layer supposed to fit?

Thermals work by retaining heat between your skin and the base layer thus thermals usually come with a snugger fit with a small gap in between. This design aids your body in maintaining your body’s core temperature when it’s cold or by releasing body heat if it’s hot.

What you want to do is ensure that your thermals are form-fitting. You should be comfortable while wearing them but they shouldn’t hang off of you. Having thermals that are too tight can slow down your blood circulation, which can make you feel colder since blood is not properly circulating throughout your body.

For the most part, thermal underwear is also meant to fit in various weather conditions, but they are typically used when it is colder. So when the indoor temperature is below 64.4 Fahrenheit, you must wear your thermal underwear under your clothes.

Regardless of temperature, what you want to remember is that excellent quality thermals will act as a thermal layer if you’re not very active; and will act as a wicking base layer if you’re moving around a lot.

thermal base layer for winter
via @icebreakernz on Instagram

How thin or thick is the material?

When picking the best thermals for your needs, it is ideal to search for that perfect blend between your thermals being thin and lightweight but can still maintain warmth.

For the most part, thermal underwear must be snug and tight since they are worn under your clothes. The bad thing about loose thermal underwear is that they bulk up under your clothes and they let your body heat to escape, which can make you feel uncomfortable.

But in general, the thicker the thermals are, the warmer you’ll be.

What is the best thermal underwear material?

The best thermal underwear material is wool because of its excellent breathability and wicking properties which are far superior compared to synthetic materials. It doesn’t dry quickly and feels very warm since it is better insulated.

The best thermals that are primarily incorporated with wool are also perfect for camping because wool is a lot less flammable. On the flip side, since wool doesn’t dry fast, it’s not really ideal for sweaty or very active users.

Is a moisture-wicking base layer needed?

A moisture-wicking base layer is important if you tend to be very active while wearing your base layer. By having a moisture-wicking base layer, you won’t easily get cold because your thermals will draw the moisture from your body.

meriwool thermals for winter
via @meriwoollayers on Instagram

Should you wear underwear with thermals?

For hygiene purposes, you must wear underwear under thermals. Thermals are not really a replacement for underwear. They are only a layer for additional warmth.


In this guide, we have compared the best thermals on the market today. We’ve broken them down into what makes them worthy such as keeping you warm and how well they prevent odor-causing bacteria. We have also discussed their comfortability and durability, and effectiveness at wicking moisture from your body.

So, when it comes to the best value for the money, our top pick for men is the Icebreaker Merino 200 Oasis Thermals. Aside from being reasonably-priced, this one is made from 100% Merino Wool and provides exceptional body heat regulation than any other men’s thermals in this guide. Moreover, it comes in four different colors. It is also incorporated with an elastic waistband for extra comfortability.

As for our top pick for women, the Smartwool Women’s Base Layer Top – Merino 250 Wool Pattern Active Crew will provide the best value for your hard-earned money. In addition to being crafted by a prominent Merino Wool clothing company – Smartwool – his base layer top provides excellent comfortability among others because of its targeted insulation and ventilation feature. Aside from that, it has excellent durability due to its flatlock seam construction, which makes it even worthy to buy.

How about you? Which thermals did you find best suited for your needs? Stay warm!