What to Wear For Outdoor Activities: The Adventurer's Guide to Layering Clothes

The clothes you wear in the backcountry could be the difference between a blissful wilderness experience or a nightmare you never want to relive.

Choose the wrong clothes and you could even get yourself into a dangerous situation dealing with a medical emergency such as hypothermia.

Outdoor technical clothing is designed to help you regulate your body temperature and stay comfortable in changing weather, temperatures, and activity levels that you might experience throughout your day or trip.

The number of outdoor brands and clothing options on the market these days can make the task of choosing what to wear for your adventure feel very overwhelming.

In places like Colorado where the temperature and weather can be erratic (e.g. the temperature dropping 40+ degrees Fahrenheit in a few hours!), you need to be prepared with clothing that will protect you from anything that mother nature has to throw at you.

As you will learn in this article, layering is the most practical and versatile methodology used by outdoor adventurers when choosing the right clothes to stay comfortable and safe in the wilderness.

Guide to Layering

How Your Body Loses Heat to the Environment

Before diving into the best methods and systems for choosing what to wear outdoors, it helps to have an understating of how your body loses heat.

The clothing you choose should aid in a process called thermoregulation, which is how your body maintains a constant core internal temperature.

Thermoregulation is directly affected by the amount of heat lost by your body to the environment, which can be minimized by knowing the right clothing to wear.

There are 5 main ways that your body loses heat:

1. Conduction

Heat loss through conduction occurs when your body is in direct contact with a surface or substance that is colder than your body, such as snow or cold water.

Water is 25 times more efficient at conducting heat away from your body than air is, which explains why you will feel much colder in 70 degree F water than in 70 degree F air.

It also means that you should avoid getting wet if you are trying to stay warm in a cold environment.

To prevent heat loss through conduction:

  • Wear a thick insulating layer (e.g. down jacket) between you and the cold surface you are in contact with.
  • Avoid sitting on or touching surfaces or substances that are colder than you, such as snow, ice, or cold water.
  • Avoid wearing wet, sweat drenched clothing by wearing synthetic fabrics that dry quickly

2. Evaporation

Evaporation is the process by which a liquid turns into a vapor (gas).

The body utilizes this process to regulate body heat naturally through sweat production.

When your body gets hot, sweat, which is mostly water, will start to accumulate on your skin.

As your sweat heats up, it will eventually turn into a vapor (gas) that carries your body heat  away from your skin and into the external environment.

When you are adventuring in hot, dry environments such as the desert, evaporation through sweat will be critical to cool your body.

However, if you are in the cold and trying to stay warm, you will want to wear synthetic fabrics that dry quickly and move sweat away from your skin.

3. Convection

When a fluid such as air or water is heated, the molecules in the fluid will start to move away from one another and the fluid will become less dense.

The heated, less dense regions of a fluid will start to rise, and the denser, cooler regions of a fluid will sink.

This process is called convection.

Your body loses heat through convection when air or water just above your skin is heated and then begins to rise.

As the heated air or water rises, it transports body heat away from your skin.

The faster air or water moves across your skin, the more efficiently conduction will transport heat away from your body and into the external environment.

For this reason, wind is the biggest factor that can speed up heat loss through conduction.

4. Radiation

Radiation is the transfer of energy through waves or particles. The heat we feel from the sun or when sitting by a fire are examples of heat transferring through radiation.

The body loses heat through radiation in the form of infrared rays.

To avoid heat loss through radiation, wear thick layers that trap radiant heat from leaving the body.

5. Respiration

When you breathe in air from the environment that is colder than your body temperature, your body will warm the air when it enters the lungs.

When you exhale that warm air from your body, your body heat is transferred into the environment.

Heat lost through respiration is usually minimal, but if your are adventuring in a very cold environment, wear a neck gaiter or balaclava over your face to help warm the air before it enters your lungs.

How Clothing Keeps You Warm

It may see obvious how clothing works, but there are reasons why some fabrics will keep you warmer or cooler than others.

Clothing keeps your body warm by trapping an insulated layer of “dead air” space (or DAS) over your skin and body.

Technically, it's not the clothing itself that keeps you warm, rather, its the dead air close to your body that is warmed by your body heat.

Different fabrics will insulate you with different amounts of dead air, resulting in different degrees of warmth or cooling.

The greater the loft (or thickness) of a garment or other insulating material (e.g. sleeping bag), the more dead air space will be created around your body, and the warmer you will likely be.

The ratio of a garment or fabric's loft relative to the weight of the garment is called it’s warm-to-weight ratio.

Down, for example, has a very high warmth-to-weight ratio because it has a high loft and it is very light compared to other materials.

Cotton, however, has a low loft and has a lower warmth-to-weight ratio than down. It also retains moisture, so cotton will also increase heat transfer away from your body through conduction if you are wet (e.g. sweating).

Outdoor adventurers in cold environments favor clothing with a high warmth-to-weight ratio, like down jackets and sleeping bags, because they are light, warm, and pack down small (though these garments come at a higher cost).

In warmer environments, look for clothing that has very little loft so that there is little dead air insulating your body. Moisture wicking, thin, loose fitting, synthetic fabrics work best in warmer climates.

How to Choose a Base Layer

Base layers are designed to keep your skin dry by quickly and efficiently wicking away moisture and sweat.

Base layers are especially important to wear in cold environments because it is essential that you stay dry in order to stay warm and avoid hypothermia.

There are two main types of materials used to manufacture base layers:

  • Wool - a natural fiber from sheep
  • Synthetic fibers - most commonly made from polyester, polypropylene, or capilene.

Choosing Cold Weather Base Layers

In cold weather, the base layer you choose should:

  • Fit close to your skin, but not so tight that you can't move comfortably.
  • Be warm. Thicker base layers with more loft will keep you warmer.
  • Be breathable and efficiently wick moisture away from your skin.
  • Feel soft and have minimal seams since it will be in close contact with your skin

Winter base layers typically come in different weights. Higher weights will keep you warmer and are better for lower activity levels and colder conditions. Lower weight base layers are better for high intensity activities and warmer conditions.

Best examples:

  • Merino wool: one if not the best natural fabrics that you can wear as a base layer in the winter. Not only does it meet the criteria above, but it is also naturally resistant to odors. Many people also report that wool keeps them warmer than synthetic base layers. Check out Smartwool or Icebreaker for some of the best Merino wool base layers. My personal favorite for all my winter activities is the Smartwool Merino 250.
  • Capilene: comprised of polyester, this synthetic fiber checks all the boxes listed above. Patagonia is known for producing Capiline, which you can check out here.

Pro Tip: Do not wear garments made from cotton while adventuring in the outdoors. Cotton absorbs moisture like a sponge and doesn’t dry quickly. It gets heavy when soaked in sweat or water, which will contribute to faster heat loss through conduction and evaporation. The only exception to this is if you are in a hot, dry environment.

Choosing Warm Weather Base Layers

While you won’t necessarily need a base layer in warm or hot weather because you are not trying to retain heat, base layers can be useful for protection and help you cool your body more efficiently.

They are especially useful in hot, dry environments such as the desert.

In warm weather, the base layer you choose should be:

  • Be loose enough to allow for ventilation so that air can move across your skin and cool you through conduction.
  • Dry quickly to cool your body through evaporative cooling.
  • Protect you from sun exposure. Sun protective clothing will have a UV rating.
  • Be made of thin, synthetic materials.
  • Light in color (e.g. white) to reflect the sun. Darker colors will absorb more solar radiation and make you hotter.

Synthetic based garments usually work best for summer base layers because they dry very quickly and are usually less insulating than wool.

My favorite for the summer is the REI Sahara button up. It is light and breathable, dries quickly, and has UPF 35 sun protection. I usually wear it over a workout tank top for extra sun protection.

How to Choose Middle Layers

The middle layer or layers are worn over the base layer and function specifically as insulating layers.  

They are designed to maximize dead air space around your body in order to help you retain body heat.

For this reason, these layers will have more loft than your base layer or outer layer.

Middle layers are usually only worn as upper body garments (e.g. sweaters, jackets).

Depending on the temperature and climate that you plan on adventuring in, you will need between 1-3 middle layers.

Also, some insulating fabrics will keep you warmer than others.

In mildly cold temperatures, you may only need one middle layer, but in colder conditions, you may have to add more layers and/or start your day with a higher loft middle layer.

There are only three main types of insulating materials used for middle layers:

  • fleece
  • wool
  • down

Fleece (or other synthetic polyester or polypropylene based garments)

Fleece is a synthetic material that comes in many different weights (densities) and thicknesses. This material is similar to wool in how effectively it insulates body heat, but it lighter, typically cheaper, and dries much faster than wool, making it an ideal choice for the outdoors. Fleece, however, is more wind-permeable than other insulating fabrics. Other trademarked names for synthetic insulating garments include: Polartec, Coreloft, PrimaLoft (though there are many others).

Wool

Natural fiber from sheep that has similar insulating properties to fleece. Merino wool is naturally odor resistant, durable, keeps you relatively warm when wet, and can be more resistant to wind than fleece. It can soak up to 30% of its weight in moisture without making you feel wet, which is how it keeps you warm in wet environments (2). Wool, however, takes longer to dry than fleece and is heavier than down or fleece.

Down

Down is also a natural material because it comes from birds. Technically, down isn’t made up of feathers; rather it is the plumage that comes from underneath the outer, protective feathers of waterfowl such as ducks or geese. Down is a favorite among outdoor adventures because goose down has the highest warmth-to-weight ratio compared to other fabrics and it packs down extremely small. Down, however, loses its loft when wet. A wet down jacket is essentially useless because it won’t keep you warm. The good news is that you can buy a hydrophobic down jacket or sleeping back. The feathers in hydrophobic down is treated with a water repellent that makes the garment more resistant to water (though not fully water-proof). Also, certain down jackets are made with synthetic down (i.e. polyester) that mimics real feathers. When choosing a down jacket, take note of its “down fill power,” which indicates its loft and warm. The higher the fill will keep you warmer than a lower one (e.g. 850 fill will keep you warmer than 600).

Guide to Choosing the Right Middle Layers

There are seemingly endless layering combinations and possibilities when it comes to middle layers so you will need to experiment with different numbers of layers and different types of insulating garments before you find the best layering combination that keeps you comfortable.

I created Table 1 as a quick reference you can use to guide you in your decision making process when it comes to choosing the best middle layers for your trip.

Table 1. Qualities of each middle layer material ranked relative to each other. Note: this is a reference to give you a broad, general overview. As you do more research, you may find exception in each category as manufacturers develop and innovate new materials and fabrics.

As a general guideline, when layering middle layers:

  • Layers with the greatest loft should be worn on the outside. For example, down jackets should be worn over your base and other middle layers (if you need them at all).
  • Layers with the least loft should be worn closest to your base layer. For example, a thin Patagonia R1 fleece works great between a base layer and a down layer.

This way, your layers get progressively “loftier” as they move away from your body.

Important: if you are looking to buy a down jacket, purchase one from a company that only uses ethically sourced down. Unfortunately, geese in the factory food supply chain become victims of cruelty and abuse. Many brands will specifically indicate if they adhere to Responsible Down Standard or Traceable Down Standards, which means that they source their down from geese that were not abused in the farming and harvesting process. Always choose these more ethically sourced options.

Best Features to Consider

You will find that may manufacturers promote special or extra features that make their products sand out.

In general, however, there are only a few features I personally find that truly make a difference when you are out in the wilderness.

Here are the top features that I think make for the best middle layers:

  • Hood: one of your middle layers should have a hood because it give you one more heat regulating option, making your layering system more versatile. I would recommend that your outermost middle layer has a hood (e.g. your down jacket). You lose a significant amount of heat through your head, and I find that hoods keep me warmer than beanies because they trap more heat. You can also wear a hood over a beanie for extra warmth. The hood on my down jacket keeps me significantly warmer than wearing a hat alone. It is my single favorite feature on my down jacket. The best hoods have hood adjusters, too, to keep the hood securely fitted to your head.
  • Hipbelt Compatibility: Some jackets have pockets that are slightly higher so that they sit above your hip belt. I am almost always wearing a hipbelt when hiking or backpacking, especially when carrying heavy camera gear. Having pockets that are above your hipbelt makes the hipbelt feel more comfortable and makes your pockets more accessible.

How to Choose an Outer Shell Layer

The outer shell is what you wear over your base and middle layers to shield you from wind, rain, and snow.

Shells come in the form of jackets and pants so that you have full body coverage from the elements.

You are only going to want to wear your outer shell when the conditions call for it (e.g. if you are in the wind, rain, or snow) because most shells are not highly breathable.

It wouldn’t make sense to wear a shell if you are breaking a sweat backpacking up a mountain on a sunny bluebird day because your sweat will have a harder time escaping through your clothes.

The best shells are:

  • Wind resistant: A shell that blocks the wind will keep you warmer by preventing convective and evaporative heat loss.
  • Water-resistant (or ideally waterproof): it is critical that your base and middle layers stay dry in order for you to stay warm. A shell will keep these layers dry and help you avoid conductive heat loss that occurs when you clothes are wet.
  • Breathable: If your activity level is high, sweat will start to accumulate and saturate your base and middle layers if it cannot escape through your shell to the outside environment. The best shells allow heat and sweat to escape so that you stay dry.

Soft Shells vs. Hard Shells

You will sometimes see outer shells categorized as soft or hard.

Soft shells are wind and water resistant and usually very light.

They will work for a light snow or drizzle of rain, but they will not protect from a heavy downpour.

Soft shells are more breathable than some hard shells, and are ideal if you are exercising in the outdoors and the forecast calls for no rain or snow.

Hard shells are waterproof and wind resistant. They keep more moisture out than water-resistant soft shells.

Not all hard shells are breathable, however. Waterproof hard shells that don't breath are usually cheaper, but they usually cause excess moisture to accumulated inside of the garment, especially if you are sweating during a high intensity activity.

Breathable hard shells are more expensive, but they are by far the best option for outdoor activities. Gore-Tex is one of the most popular materials used to make breathable hard shells.

Insulated Shells

Some outer shell jackets and pants come with built in insulating materials to keep you warm on top of protected from the elements.

These shells allow you to reduce the number of middle layers that you will need to stay warm are usually marketed as ski or snowboard jackets.

While it is convenient to have both your middle and outer layers integrated into a single jacket (especially if you go from indoors to outdoors frequently such as at a ski resort), these jackets are not ideal for most outdoor adventures.

This is because the fewer layers you have, the less versatility you will have to layer up or layer down throughout a day of changing temperatures and activity levels.

While it will cost more in the short term to purchase a separate shell fro you middle layers, it will pay off in the long run in terms of your comfort and happiness in the backcountry.

Bonus Features to Look For

When shopping for a technical outer shell, the best upgrades include:

  • Taped Seams: Taped seams will make a hard shell 100% waterproof because it prevents water from leaking through the seams.
  • Vents: some shells have zippers on the sides/pits that allow you to vent heat from your body. Vents will make your shell more breathable and help you regulate your body temperature.

The Layering Concept

A simple system called layering is the best way to quickly and easily decide what clothing will be best for your trip.

The concept of layering was first taught to the outdoor community back in the 1980’s by the outdoor company Patagonia after experimenting with, testing, and designing fabrics that functioned optimally for mountaineers (1).

Layering is the most versatile, efficient, and functional way to dress in the outdoors.

Layering involves wearing 3 main layers:

  1. A base layer: an inner layer against the skin that transports moisture away from the body to reduce evaporative and conductive heat loss.
  2. A middle layer: designed for insulation by trapping radiant body heat and preventing conductive heat loss. In cold condition, you can wear more than one middle layer.
  3. An outer shell: to protect you from convective and conductive heat loss due to wind, water, and other elements.

This three layer system is optimal because it allows you to add or remove layers according to your thermoregulatory needs in a changing environment.

In other words, if you get too hot, you can remove layers, and if you get too cold, you can add layers.

This way you can easily maintain a comfortable body temperature.

When tailored to your individual needs, the three layer system is also designed to protect to from nearly every outdoor environment, temperature, and weather scenario.

Factors that Will Affect Your Personal Layering System

The 3 layer system is simple and versatile, but it will require a little experimentation on your part to dial it in for your own needs.

Take into consideration the following factors before you choose specific layers for your adventure:

  • Activity level: The higher your physical exertion, the more body heat you will generate. Higher activity levels produce more body heat and will require fewer, less insulated layers. You will likely need more layers when making your coffee outside in the morning than you will when you are backpacking to the top of a mountain.
  • YouR size: Larger people generally lose less body heat than smaller ones (e.g. children) because of their surface area to weight ratio. Smaller people are more likely to need extra layers and/or heavier, more insulated layers to keep them sufficiently warm.
  • Your gender: The average woman generates less body heat than the average man because women typically have lower metabolisms than men. This explains why, when in identical environments, women tend to be colder than men. Women often need thicker, heavier layers and more of them to stay warm.
  • Your environment/climate: The destination you plan to adventure in will largely determine which layers are best. A warmer, drier climate will require fewer, lighter layers as opposed to a colder, wetter environment. Humidity will make your body feel colder because moisture in the air will draw your body away more quickly through conduction. Windy and/or rainy environments will require special protection in the form of a shell to prevent heat loss through convection and conduction. Some environments (like the mountains) have highly variable temperature from day to night.

Depending on these factors, you should plan on taking off and adding layers throughout the day.

Always carry the number and type of layers that will protect you from the most extreme temperature and weather that you could potentially encounter.

This means that you will usually have some "just in case" layers in your pack if the conditions call of them.