Warmest Base Layer: Searching For The Ultimate Product

Running base layers
Written by Dennis Owens

There is an age old debate among people who like to go to the outdoors: what’s worse, the heat or the cold? It’s a question that will never have an answer since it depends so much on personal preference, but each one has its own dangers that must be prepared for in order for you to stay not only comfortable but safe while out in the wilderness.

We are going to be focusing on cold weather and on perhaps the most important thing you can do to stay warm in cold temperatures: layers. Having the warmest base layer as possible is of utmost importance as it will help you stay dry and will help trap in your body’s warmth.

There are lots of different products out there that are made from different materials and do different things. Finding the best layer for cold weather will depend a lot on what activity you are planning to do and where you are going to do it.

Base layers intro

This will help you understand what you need and will allow you to be fully prepared to take on the elements. We will talk about this as we go over the different options on the market so that you can get an idea of what might be best for you.

Tips for staying warm in the cold

Anybody who has had experience hiking, camping, hunting, skiing, etc. in extremely cold temperatures knows how dangerous they can be and also likely knows that once you start getting cold it is very difficult to get warm again. This is why base layers are so important.

They help to trap in the warmth your body generates so that your outer layers, which work to ward off the cold from outside, can be more effective. Before we go further into the different features of thermal gear and what to look for, let’s go over some general tips for staying warm in the cold so that you can defend yourself as best as possible from freezing.

Build your layers

It is always important to start off your adventure with fewer layers and then build up as you go. When you are in the warmth of your home or your car you do not want to put everything you have on and then go outside. This could leave you in a situation an hour later where you feel cold but don’t have anything left to put on.

Layering for the outdoors

You want to start off with enough layers to make sure that you trap in the warmth and are protected, but you always want to have something else with you to put on in case you underestimated the elements and find yourself a little chilly after setting out on your adventure.

This is a tricky game to play, though, because if you let yourself get cold you might have trouble getting warm again. You need to be very mindful of how you are doing temperature wise so that you can prevent any situation that might cut your time in the outdoors short.

Shed layers cautiously

Maybe you overestimated how cold it is or you are doing something that requires a lot of movement and you find yourself getting warm. The temptation might be to rip off a few layers and get cool so that you can keep going, but this can actually be quite dangerous and should be avoided if possible.

If you feel yourself getting warm, unbutton some of your jacket’s or remove one layer and then wait to see how you feel. You may feel warm because of all the equipment you are wearing, but over exposing your body to the cold could cause a rapid drop in temperature that might be difficult to overcome.

Think about when you go running on a fall day in shorts and a t-shirt. While you are running you feel warm but as soon as you stop you start to get very cold. Another thing you could do is to just take a break. If you are doing something active and sweating, it might be a good idea to just stop for a little and let yourself cool down.

Feeling hot in these conditions might make you want to remove clothing to enjoy the cool temperatures, but control these desires so that you can safely monitor your body temperature and continue to enjoy whatever it is that you are doing.

Sock! Socks! Socks!

Your feet are likely one of the first extremities to get cold when you are out in the wilderness. Some good insulated boots are important to helping prevent this, but so are the socks that you wear. You want them to be warm but also dry.

If your feet get wet either from sweat or from snow or rain, they will quickly get cold and your experience will turn unpleasant in no time. Experienced hikers, campers, hunters, etc. should always carry an extra pair of socks with them so that they can change into them in the event their feet get wet.

Dont forget the socks

Cold and wet feet is a serious problem, it brought down most of Napolean’s army when they tried to invade Russia, and being prepared to act when you notice it happening could be the difference between a positive memory and a disastrous one.

Keep your core and your head warm

Next to keeping your feet warm, making sure your core stays at the right temperature and keeping your head covered should be your top priorities. There’s an old wives tale that you’ve surely heard your mother say at least once or twice that you lose something like 80 to 90 percent of the heat of your body from your head.

This is most likely not scientifically true, but it is no doubt that keeping your head and your ears covered is an essential part of staying warm. Also, you should go out of your way to maintain the temperature of your core. If you don’t have enough to cover your whole body, make sure to keep this part as insulated and as warm as possible.

Keep upper body warm

This will help keep the rest of your body warm as blood circulates around it. It’s obviously important to maintain all parts of your body warm, but keep this in mind if you have limited supplies or if you find yourself in an emergency. Many of the base layers we are going to be looking are designed specifically for this purpose.

What to look for in base layers—important features

Now that we have gone over some key ways to stay warm when you are in cold temperatures, let’s take a look at some of the differences between the different products that are on the market so that you can start to get an idea of what is the best one for you.


Like any clothing product, the material from which it is made will dramatically affect its performance. Each fabric that you will find on the market has its own distinct advantages and disadvantages.

The type that you choose will have a lot to do with the activity you plan to do with the gear. Let’s take a look at the most common types of fabric on the market and go into some detail about some of their differences.


Synthetic fibers like nylon, acrylic, and polyester are commonly found in these types of products. Perhaps the most common one for thermal gear is polyester. What makes it stand out against other fibers, both synthetic and natural, is its resistance to moisture and its ability to dry quickly.

Base layer materials

If you think of your typical Under Armour or similar products, they are usually made with synthetic fiber. Because of this quick-drying property, these fabrics are great for people that are planning on being active in the cold weather.

As you sweat, this material will wick away the moisture and dry quickly so that you won’t get cold from being wet. That being said, synthetic materials tend to be thinner and are not as warm as other fabrics, which we will discuss in the next section.


Some consider wool to be nature’s warmest fiber. Garments made of synthetic materials with the same thickness will not be anywhere near as warm as something made of wool.  What’s also nice about wool is that it is a natural fiber and breathes easily.

This allows moisture to evaporate inside the fabric and helps you maintain a steady body temperature. Wool is also naturally antibacterial so it can be worn more than a few times in a row without accumulating odor or needing to be washed. This is a particularly nice feature for hunters since they don’t have to worry about giving off unwanted scents.

Wool base layer

One downside of wool is that it can be itchy or scratchy. Some types of wool, such as merino wool, do not have this characteristic, but others do. For this, it might be a good idea to try on the garment before purchasing it to make sure that it doesn’t bother you when you go to wear it.


Whether or not to buy a base layer that is made of cotton is a bit controversial. Most experienced hikers/campers would probably say no since it is not particularly good at wicking away moisture. When it gets wet it has a tendency to stay wet and this can be a big problem if you are going to be active in colder temperatures since you will likely be sweating and this could cause you to get cold.

That being said, there are quite a few products on the market that use this material, but what they often do is combine it with some other fabric. Cotton is comfortable, breathable and doesn’t itch like wool.

You might find a piece of clothing that has cotton on the inside and another material on the outside or vice versa. This makes cotton a little better, but if you are going to be active or in extreme conditions, it might be a good idea to look at some of the other materials available.


Once you’ve figured out the material that is best for you, the next thing you should look at is the weight. In general, there are three different categories: light, medium and heavy. The difference between each one is pretty intuitive.

Base layer weight

The lightweight materials are better for more active people as they will dry faster and be less warm while the heavy weight garments will be better designed for trapping heat and might not be as good at wicking moisture or drying. Think about what it is you will need this base layer for and that will give you a good idea as to the weight that is best for you.


After deciding the weight of your base layer, you will need to get an idea as to the fit you would like. Again, this has a lot to do with what you need this garment for so if you have that pretty clear it should be easy to figure out what type of fit you would like.

But this isn’t the only factor, it also matters what you will be most comfortable in. We are going to go over the three most common fits out there so you can get an idea of which is best for you.


It’s all in the name. Loose fitting base layers will hang off the body, which makes them more comfortable, but has the possibility of being less warm. Products with a loose fit will feel much like your normal clothing. It is good for moderate activity and for moderate conditions.


A snug fit is tighter than the loose fit but not as tight as the athletic fit. Because of this, it can be considered a universal fit.

It is sufficiently tight to provide warmth and leaves enough room in between it and the skin to allow for breathing and moisture wicking. If you are going to be active or in colder temperatures this is likely a good choice for you.


This fit is best for people who most identify with its name: athletes. It is characterized by a very tight fit and is usually the fit associated with garments made from synthetic fibers. It is great if you plan to be very active as it will fit tightly to your skin and won’t be in your way.

The synthetic fibers wick away moisture and will keep you dry and warm. This fit can be a bit uncomfortable for people not used to it, so keep this in mind if you decide to go for it since it will likely take some getting used to.

What’s available?

There is a lot to consider when thinking about which is the best base layer for you, but what you are going to use it for and where you are going to be are key things to know to help you make your decision. We are going to take a look at some of the products available on the market to give you an idea of what might be the best option for you.

Duofold Men’s Heavyweight Double-Layer Thermal Shirt

Duofold Mens Heavyweight Double-LayerWeight: 1 pound

Dimensions: Size S-XXL

Material: Polyester

Light, medium or heavy: Heavy

Fit: Snug

Top or bottom: Top

Best use: Colder temperatures and moderate activity

This thermal shirt does a good job of combining warmth and moisture wicking. It is double layered and made of synthetic materials so you can use it while being active in cold temperatures. It is a snug fit, which makes it practical for almost all uses and the manufacturer has gone a little further to make it more comfortable by removing the tags and by including a drop tail so that it is easier to keep the shirt tucked in.

The garment is technically 94% polyester and 6% Spandex. The little bit of Spandex gives the shirt a tighter fit and helps make it more comfortable. All in all, this is a solid base layer for colder temperatures and for people who are likely to be active in them.

ColdPruf Men’s Authentic Dual Layer Long Sleeve Wool Plus Crew Neck Base Layer TopColdPruf Men's Authentic Dual Layer Long Sleeve Wool Plus Crew Neck Base Layer Top

Weight: 1 pound

Dimensions: Size S-3x large tall

Material: 100% cotton inside, 40% merino wool, 10% nylon outside

Light, medium or heavy: Heavy

Fit: Snug

Top or bottom: Top

Best use: Extreme cold temperatures with low to medium activity

This is a great base shirt for very cold temperatures. It has two layers, the inner one made of cotton and the outer one made of a mix of wool and nylon. The use of wool helps to make the shirt very effective in cold temperatures and by mixing it with nylon they have made it a little better at moisture wicking than you might expect.

It has a snug fit, which should make it plenty comfortable to wear while also being effective at keeping you warm. The one thing to keep an eye out for is that the inside of this garment is made from cotton.

We mentioned earlier that cotton has a tendency to stay wet longer and therefore isn’t the best option if you are going to be using the shirt for high activity. If not, and all that you are looking for is some protection from the cold, you may have found the perfect shirt for you.

Under Armour UA Base 4.0 Crew – Men’sUnder Armour UA Base 4.0 Crew - Men's

Weight: 1 pound

Dimensions: S-XXXL

Material: Synthetic (fleece-grid)

Light, medium or heavy: Heavy

Fit: Snug

Top or bottom: Top

Best use: Cold temperatures and high activity

Many of us know Under Armour for its sports equipment and this particular product is no different. It is made with the company’s own fleece-grid technology, which is supposed to make it extra warm while still being effective at wicking away moisture.

This is why it is good for use in extreme cold when you are going to be active. The fabric does a good job of keeping the moisture of your body and actually allows for your body to warm up any moisture it gives off, which goes even further in maintaining your body temperature.

It fits snug; it doesn’t have an athletic fit, which helps maintain easy motion. In general, if you think you are going to be moving around in very to extremely cold temperatures this could be the perfect shirt for you.

Woolx Men’s Merino Wool Shirt – Moisture Wicking Heavyweight Merino Base LayerWoolx Men's Merino Wool Shirt - Moisture Wicking Heavyweight Merino Base Layer

Weight: 1 pound

Dimensions: S-XX Large

Material: 100% merino wool

Light, medium or heavy: Heavy

Fit: Snug

Top or bottom: Top

Best use: Extreme cold—hunting and skiing

This is a great shirt for anyone that is going to be in very cold temperatures. Being made from 100% merino wool means that it will be plenty warm enough even in the most extreme conditions.

Woolx Mens Merino Wool Shirt is great for hunters and other outdoorsmen since the naturally wicking and odor prevention properties of wool will keep you warm, dry and free from smells. It fits snug, which makes it even more effective against cold temperatures. It might not be as effective in wicking as some synthetic materials, but it makes up for it by being so warm.

If you are going to be doing some outdoors sports in very cold temperatures this is a great option for you. It does come with its price, at almost $100 it is more expensive than many other products, but its performance should make it worth it.

Craft Women’s Extreme Concept Piece Long Sleeve Base Layer ShirtCraft Women's Extreme Concept Piece Long Sleeve Base Layer Shirt

Weight: 9.1 oz

Dimensions: S-XXL

Material: 100% polyester

Light, medium or heavy: Light

Fit: Snug

Top or bottom: Top

Best use: Mild temperatures, high activity

This layer, designed specifically for women, is great for anyone who is planning on doing any type of activity in milder temperatures. It is made from polyester, which means it will stay dry easily and will wick away moisture as you sweat.

However, it is not a great layer for colder or extreme temperatures. Being lightweight, it won’t offer too much protection against extreme conditions. Mild activity and mild temperatures is the perfect situation for this type of garment.

ColdPruf Men’s Dual Layer Long Sleeve Union SuitColdPruf Men's Dual Layer Long Sleeve Union Suit

Weight: 1 pound

Dimensions: S-XXL

Material: 100% Cotton inside and 65% Cotton, 25% Merino Wool, 10% Nylon on the outside

Light, medium or heavy: Heavy

Fit: Snug

Top or bottom: Both

Best use: Very cold to extreme cold/low to medium activity

This full body base layer is exactly what you need to defend yourself against extremely cold temperatures. It will cover your entire body in thick, double-layered material that will trap heat and keep moisture out. The inner layer is made of cotton so you can be sure it will be nice and comfortable, but this means it might get and stay wet easier.

This is why this product is best for low to medium activity. The outer layer is a nice mix of wool, cotton and nylon, which help it to fit snugly and comfortably against your body. This layer will fit nicely underneath the rest of your winter gear and will provide you with a great base to stay warm even in the coldest of temperatures.

Under Armour Men’s Extreme Base BottomUnder Armour Men's Extreme Base Bottom

Weight: 1 pound

Dimensions: S-XXXL

Material: 100% polyester

Light, medium or heavy: Heavy

Fit: Snug

Top or bottom: Bottom

Best use: Cold to extreme cold with moderate to high activity

If you are headed out into extreme conditions and are really worried about staying warm, it might be a good idea to extend your base layer to your legs as well. This product by Under Armour gives you that option and will protect your legs against the cold while preventing moisture build up.

The polyester will wick away any sweat and will dry quickly when wet. However, since polyester is synthetic it might build up some odor and need to be washed more frequently. All in all, this is a nice option for someone who is going to be active and wants to stay warm in harsh cold conditions.

Layer up!

With the right amount of layers and proper preparation, you can tackle any temperature. Hopefully, the information provided here has reminded you of why it’s so important to stay warm and how to do so.

Base layers for skiing

There are a variety of different products out there and knowing what you will be doing and in what conditions is key to you finding the best base layer for cold weather.

Have any experience with the products we reviewed? Any tips that we forgot to mention? Let us know so we can share, but otherwise, layer up and get out there. Stay warm!


Dennis Owens

Dennis Owens is a graduate of National Camping School and REI Outdoor School. He knows everything about what gear to take with you, how to plan your trip to stay safe and what to do if you get lost in the mountains. We are lucky to have Dennis with us as he is a ‘walking encyclopedia’ when it comes to the wilderness.