Best Warmest Thermal Underwear For Extreme Cold Weather

The warmest thermal underwear for extreme cold will keep you dry and retain your warmth in hiking, climbing, and mountaineering conditions. Moreover, many choose to wear such clothes indoors due to being extraordinarily stretchy and soft, like a second skin.

Thermal underwear for men and women is not a luxury. In icy conditions, they can save your life. The materials and their moisture-wicking properties, such as their weight, are essential factors. You can plan suitable clothing for your outdoor excursions with all our information.

We, too, use them in our excursions, and with this research, we will present you with what you need to know when you buy thermal underwear for extreme cold and the factors that govern such a decision. On top of that, we researched the five best thermal underwear options to help you decide.

Comparison Chart: Warmest Thermal Underwear for Men and Women

Here are the five best thermal underwear products we reviewed and compared for you. Further down the article, you will find our preference.

IMAGE PRODUCT
Best Warmest Thermal Underwear For Extreme Cold Weather 1Best Warmest Thermal Underwear For Extreme Cold Weather 2 1. Thermajohn Men’s Ultra Soft Thermal Underwear Long Johns Set
  • Ultra Soft Polyester, Spandex
  • Lightweight
  • Men
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Best Warmest Thermal Underwear For Extreme Cold Weather 3Best Warmest Thermal Underwear For Extreme Cold Weather 4 2. Under Armour Men’s HeatGear 2.0 Leggings
  • Polyester, Elastane
  • Lightweight
  • Men
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Best Warmest Thermal Underwear For Extreme Cold Weather 5Best Warmest Thermal Underwear For Extreme Cold Weather 6 3. Thermajane Thermal Underwear for Women Ultra Soft Long Johns Set with Fleece Lined
  • Polyester, Spandex
  • Lightweight
  • Women
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Best Warmest Thermal Underwear For Extreme Cold Weather 7Best Warmest Thermal Underwear For Extreme Cold Weather 8 4. DAVID ARCHY Men’s Soft Winter Warm Base Layer Top & Bottom
  • Acrylic, Rayon
  • Heavyweight
  • Men
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Best Warmest Thermal Underwear For Extreme Cold Weather 9Best Warmest Thermal Underwear For Extreme Cold Weather 10 5. FITEXTREME MAXHEAT Mens Thermal Underwear Long Johns Set with Fleece Lined
  • Polyester
  • Lightweight
  • Men, Women
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Warmest Thermal Underwear For Extreme Cold

Let’s examine each option individually and see where they stand firm and how they compare.

1. Thermajohn Men’s Ultra Soft Thermal Underwear Long Johns – Best Thermal Underwear Lightweight Choice

Best Warmest Thermal Underwear For Extreme Cold Weather 11Best Warmest Thermal Underwear For Extreme Cold Weather 2

Thermajohn Men’s Ultra Soft is a lightweight men’s thermal underwear set with a thermal top and bottom. The soft polyester and spandex combination in materials keeps moisture away, so you stay dry, and you feel fresh all day long.

The materials technology is odor resistant in many ways. On top of preventing smell, stop odor-causing enzymes from sticking to your skin.

This men’s thermal set is a 4-way stretch and sticks to your skin without hindering your movements or causing rash frictions. You can wear it indoors and outdoors. It is durable with seams that hold so they won’t rip prematurely. It is like a second skin and is tagless to avoid any irritations. The crotch area comes without zippers, making it far less challenging to use when nature calls.

Specifications

SizeX-Small to 4X-Large
ColorBlack, Green, Navy, Gray
MaterialUltra Soft Polyester, Spandex

Features

  • Fit
  • Moisture-wicking
  • Comfortable 
  • Lightweight 
  • Durable
  • Soft
  • Excellent at absorbing odor
  • Breathable
  • Very stretchy

What We Like

We love the snuggly feeling this thermal underwear for extreme cold provides, along with the easiness of the buttons, all placed in the right places. It is soft, and you can wear it outdoors or even sleep in it and have a very comfortable night.

What We Don’t Like

Due to it being a single long-form thermal suit, you may want to check your dimensions twice before buying. But that is the case with whole body thermals for extreme cold weather.

Pros

  • Snuggly warmth feeling.
  • Excellent duofold materials.

Cons

  • Double-check your body dimensions.

2. Under Armour Men’s HeatGear 2.0 Leggings

Best Warmest Thermal Underwear For Extreme Cold Weather 13Best Warmest Thermal Underwear For Extreme Cold Weather 14

The Under Armour men’s HeatGear leggings are made from tough, lightweight fabric, with all the performance benefits of UA Compression. The materials wick sweating very fast—these thermal leggings underwear for the extreme cold stretch in every possible direction.

Cleverly designed gusset and inseam panels aim (and provide) excellent ventilation. The overall design vastly reduces abrasion while it increases durability.

The highly elastic waistband is tagless and keeps the leggings in place without a squeezing feeling. Its compression level is considered an ultra-tight, second-skin fit.

Specifications

SizeS to 3X-Large Tall
ColorGraphite, Black, Carbon
Material79% Polyester, 21% Elastane

Features

  • Fit
  • Moisture-wicking
  • Comfortable 
  • Lightweight 
  • Durable
  • Soft
  • Excellent at absorbing odor
  • Breathable
  • Very stretchy

What We Like

This thermal underwear fits exceptionally well and doesn’t block movement at all. The UA compression technology helps relieve soreness by reducing your body’s time to flush excess lactic from strenuous exercise.

What We Don’t Like

If you are into yoga, they might be somewhat “revealing.” It’s a pity since they are highly flexible.

Pros

  • Excellent compression.
  • Very elastic in the right places.
  • Moisture wicking.

Cons

  • Too revealing without pants.

3. Thermajane Thermal Underwear for Women Ultra Soft Long Johns Set with Fleece Lined

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Thermajane thermal underwear for women for extreme cold sets is lightweight and breathable. It fits like a gentle glove, and that means comfort.

The two-piece women’s thermal underwear has an elastic waistband at the bottom, wicking away moisture.

It is fleece-lined, and the 4-way poly-spandex stretch allows a full range of movement.

The overall fit won’t bunch up under your clothes, as they follow the shape of your body. You can wear this thermal underwear in your house or outdoors without extra garments.

Specifications

SizeXX-Small to 3X-Large
ColorMultiple colors
Material92% Polyester, 8% Spandex

Features

  • Excellent Fit
  • Moisture-wicking
  • Comfortable 
  • Lightweight 
  • Durable
  • Soft
  • Excellent at absorbing odor
  • Breathable
  • Very stretchy

What We Like

We think that the 2-piece with crew neck concept is very convenient. You can get them in multiple colors and do your combinations. You can always wear only the top or the bottom, depending on the amount of cold you encounter or whether you are indoors and stay warm.

What We Don’t Like

They don’t have the compression other thermal underwear have. Compression is extra when you plan to wear such clothes for sport, hiking, mountaineering, or snowshoeing.

Pros

  • Moisture wicking.
  • Two-pieces flexibility.
  • Lots of colors.

Cons

  • Lack of compression for sports.

4. DAVID ARCHY Men’s Soft Winter Warm Base Layer Top & Bottom

Best Warmest Thermal Underwear For Extreme Cold Weather 17Best Warmest Thermal Underwear For Extreme Cold Weather 8

Similar to Thermajane’s thermal underwear for women set, the David Archy Base Layer Top & Bottom has the same and even more qualities.

It is stretchy and heavyweight and comes with double-faced fleece lining. That makes it ideal for a set of thermal underwear for extreme outdoors cold weather.

The functional front opening is convenient, and the close-fitting helps you stay warm.

The knee and elbow areas are enhanced as more friction is there with the extra clothes you wear when trekking. The crew neck design also provides less friction and zero obstacles around your neck when wearing an extra jacket or another base layer (depending on the cold).

Specifications

SizeSmall to X-Large
ColorBlack, Navy Blue
Material66% Rayon, 26% Acrylic, Spandex

Features

  • Fit
  • Comfortable 
  • Heavyweight 
  • Good at absorbing odor
  • Thick and soft
  • Breathable
  • Durable
  • Very stretchy

What We Like

Its lining provides extra warmth, much needed for icy weather activities. We also like the additional protection at the knees and elbows. Also, we like that it comes in two pieces for this thermal underwear, so you can choose which to wear depending on the circumstances.

What We Don’t Like

Too warm to wear indoors, compared to others.

Pros

  • It is specialized for cold outdoors.
  • Extra knees & elbows protection.
  • Two pieces to wear independently.

Cons

  • Too warm to wear indoors.

5. FITEXTREME MAXHEAT Mens Thermal Underwear Long Johns Set with Fleece Lined

Best Warmest Thermal Underwear For Extreme Cold Weather 19Best Warmest Thermal Underwear For Extreme Cold Weather 10

Due to its materials, the Fitextreme Maxheat Thermal Underwears is another excellent solution for extreme cold weather.

Its fitting is rather good, with an elastic waistband and 4-way stretch. The flatlock seams help not get any rash due to friction during hiking and such activities. Depending on the circumstances, you can wear the whole set from this thermal underwear or only the top or bottom.

It is rather suitable for sports and outdoor activities. It can be worn all day long and keep its freshness reasonable. Check here for Fitextreme Maxheat Women’s Thermal Underwears.

Specifications

SizeS to XX-Large
ColorBlack, Navy, Gray
Material92% Polyester, 8% Polyurethane

Features

  • Fit
  • Moisture-wicking
  • Comfortable 
  • Lightweight 
  • Durable
  • Excellent at absorbing odor
  • Thick and soft
  • Breathable
  • Very stretchy

What We Like

Its compression is not of the sports type but will make you look good. But the warmth it provides is of its strength, ventilation, and moisture-wicking capabilities.

What We Don’t Like

Too warm to wear indoors too, compared to others

Pros

  • Very warm for extreme outdoor cold.
  • Two pieces to wear independently.
  • Moisture-wicking.

Cons

  • Too warm to wear indoors.

Our Choice for Warmest Thermal Underwear For Extreme Cold Weather

We find the Thermajohn Men’s Ultra Soft Thermal Underwear set as the best thermal underwear choice for men and the same thermal underwear for women. It has all the qualities most of the other options have, and its ultra-soft material is a plus.

It can be compressed and take less space while adding a mid-layer if the situations are beyond extreme cold. You need to be flexible with dressing outdoors and wear layers to remove those layers as conditions change.

You can check more details and prices for this option from here.

What is Thermal Underwear?

The purpose of thermal underwear for extreme cold is to keep you warm under harsh outdoor very low-temperature conditions. When you plan to stay outdoors (i.e., winter camping) for more than one day, and it’s freezing outside, you need thermal underwear.

Thermal underwear is usually a set (or you can make a set by combing a different thermal top with another thermal bottom). Tops come with long sleeves and bottoms with long pants. You may also hear them as “long johns.” You wear them directly on your skin and depending on the temperature. You may add more layers between your thermal underwear and your jacket or pants.

Due to movement, legs tend to be warmer when you hike or climb. However, the top part of your body is not producing the same amount of heat. That is why many prefer to wear a thermal top while walking and the bottom for sleeping outside.

When exposed to cold wind or rain, your torso and legs must always be warm, especially during short resting breaks.

Thermal underwear for extreme cold differs from standard underwear (or underpants). As you wear them directly on your asking, they must be moisture-wicking and quick drying. That means pushing moisture from sweat away from your body and fast. The quick-drying factor is also essential as you don’t want all that moisture trapped between your underwear and a mid-layer or jacket.

That moisture will cause discomfort or the risk of catching a cold in freezing temperatures. They are not the layers you will put on and off during outdoor activities. Thus, they must be of good quality and suitable for the temperatures you plan to be in.

Thermal underwear for extreme cold must be made from materials that usually relate to synthetics fabrics or merino wool base layers. The ones for far extreme cold come with fleece lining for extra protection.

What to Look for in the Best Thermal Underwear for Cold?

Three main factors influence any choice for thermal underwear. These relate to how they should fit, the type of fabric and materials, and their weight depending on the temperature. Other than that, some thermal underwear comes with extra padding at the knees and elbows, making them more durable and adding more fabric to areas that must move freely.

How to Best Fit a Thermal Underwear?

The term here is skin-tight. You don’t want loose thermal underwear, which influences their capability to keep you warm and act as moisture-wicking. If they don’t fit exactly on your body, the flexible fabric can obstruct your movement or even cause a rash from friction.

If they are small, they will cause lots of friction and wear out fast. Skin-tight means that your movement is not obstructed, and you don’t feel discomfort in your body. If the underwear cuts your blood circulation, it is the wrong size.

Thermal underwear should be soft and ideally without protruding seams—a zipper for when nature calls are necessary. As shapes differ, it is best to buy gender-specific thermal underwear for men and women.

Finally, union suits (one-piece long johns) are not for everyone. Avoid the ones with buttons, as buttons may cause discomfort when walking.

What Kind of Thermal Underwear Fabric Is Best?

Thermal underwear for extreme cold is as good as its fabric.

The lightweight Merino wool base layer is the latest technology in thermal base layers. Its properties are excellent. It is moisture-wicking and warm without being heavy.

The standard wool is, of course, warm but is thicker, heavier, and usually causes itches.

Synthetic fabrics (i.e., polyester, polypropylene, rayon, nylon, spandex, etc.) are an excellent and cost-effective option, with moisture-wicking performance, soft-touch, and colossal flexibility, and stretch capabilities.

Avoid cotton at all costs as they keep moisture in and take forever to dry. It loses any stretch capacity when wet and sticks to your skin. Cotton is not the solution for any cloth for outdoor activities for the same reasons.

Which Thermal Underwear Weight is Suitable?

There are usually three main types of weight for thermal underwear. These are lightweight, midweight, and heavyweight. Lightweight is suitable for cold weather or even for wearing your thermal indoors. But to get highly insulated, the best thermal underwear for cold will be either midweight or heavyweight.

A simple rule to follow is this. When you plan to encounter freezing weather and wind, go for the heavyweight. Below that, you can use midweight or lightweight in milder cold conditions.

Thermal underwear does not produce heat. The combination of materials and fabric properties is intended to keep moisture away from your body, so your body doesn’t get cold from that moisture. With an extra mid-layer and a jacket, you will achieve the warmth level needed per circumstance.

Remember that you can constantly shift between “too many” layers in icy weather, but it will not be that comfortable if you are dressed lightly, as you can’t wear more than one jacket, right?

FAQs for Thermal Underwear For Extreme Cold Weather

Which Thermal Underwear should I get for Intense Activity?

A lightweight to midweight (tops) should suffice, depending on the weather and temperature conditions. If you generate lots of body heat with intense, then you need moisture-wicking. A heavyweight may cause excessive sweating, but that depends on the temperature. You need to consider the temperature when you take a break from the activity.

How to clean Thermal Underwear?

Only follow the manufacturer’s instructions. 99.99% of the time, no ironing is needed.

How to wear 2-piece Thermal Underwear for Cold Weather?

Tuck the top in your bottom. In that way, you avoid circulating cold air in the area if your top moves up.

Is Thermal Underwear only for Outdoors?

The mid-weight and heavyweight ones are primarily for outdoors due to the warmth level they provide. Lightweight ones are perfect for outdoors and in-house. You can always wear them indoors, of course. It is up to you.

Should I wear Underwear under Thermal Underwear?

Technically, thermal underwear is underwear by itself. Men’s thermal underwear has an opening for a reason too. Its materials and fit are meant not to create any irritations and help you move freely while keeping you dry. When you are outdoors for hiking and climbing, the cloth that is next to your skin is the one that moves a lot. Wear cotton between your skin, and your thermal bottom may rise, twist, and change positions. That is very uncomfortable and difficult to adjust in cold weather conditions, i.e., removing gloves, lifting a jacket, etc. Our opinion is to wear thermal underwear only. It is best to have multiple sets and change daily (for multi-day trips) than to have all these troubles when walking. If you have to wear underwear, make sure that they stick to your skin and are elastic enough not to shift from their original position.

At What temperature should one wear Thermal Underwear?

It depends on the circumstances. A rule of thumb is to wear them when you are outside for more than 30 minutes, and the temp is below 50 degrees Fahrenheit. If you are not doing intense activities, thermal will work best.

How many pairs of Thermal Underwear do I need?

The materials of such underwear are moisture and odor wicking. One pair is enough for a single day of hiking under cold conditions. Nevertheless, you can’t wear one pair for many days if you sweat.

Now you have all the information on choosing thermal underwear for women and men. Whether with a wool base layer, merino wool, or any synthetic fabrics, long john or not, the point is to keep you warm, dry quickly, and be moisture wicking.

For wintertime, you need long thermal underwear and not short-sleeved. Sustaining a suitable body temperature is crucial when you are outdoors.

If you liked this article about the warmest thermal underwear for extreme cold, consider checking out our other reviews below:

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