There is a famous saying which goes: “There is no such thing as bad weather, just bad clothing” and out on your trek or hike, this cannot be truer.
The clothing you take on your trip does a lot more than just protect your modesty. It is the barrier between you and the outdoor elements, and unless you work outdoors regularly, the sad fact
is your body is not used to these elements and will feel stressed by them.
It could be just simple discomfort, but it could also be far more serious. Selecting the right clothing for your trip must be more than just grabbing what’s in your closet or choosing the latest fashion. In this section we will look at the principles of clothing selection and learn to understand what makes up good outdoor clothing.
In this section we are going to look at some of the basic design features of outdoor clothing. It must be remembered that clothing is very much a personal choice and there is seldom a ‘perfect’ garment which suits everyone – hence the large selection available in stores.
We will try to suggest features to look for, but you will need to decide if these are what you like, and if they are appropriate for the types of trip you do. If you have any personal insights or suggestions, we can add in her – feel free to use the quick comments box and let us know.
In the outdoors, this is just a fancy way of referring to your underwear, with a higher price tag. Seriously though, your Base Layer is the layer of clothing closest to you skin which is designed to partially keep you warm, but also to remove moisture from your skin keeping it dry. Modern base layers are made from Synthetics, Silk or Wool, with the synthetics being the most common. We must distinguish between the base layers or ‘thermals’ you buy at an outdoor store from those bought at a standard clothing store. In some cases, they look similar, but proper outdoor thermals are technically far more advanced as well as more expensive. Technical Thermals will be made of a fabric which will remove moisture from your skin, but dry very fast as the material does not absorb and hold moisture, it repels it. This is where the poly-cotton thermals bought in your local store differ. Poly-cotton works great on a winter’s night at home, but out in the outdoors, the cotton will absorb moisture and hold it, keeping you damp. The cotton is ‘brushed’ to give it that nice cosy feel, but it’s still cotton.
A good set of thermals will last a long time if you care for them, so are a good investment. Most decent thermals are also designed so you can walk around in them at the end of the day without embarrassment whilst your other clothing dries.
If you are on a seriously low budget and cannot afford good quality thermals, the high street store variety versions will be better than nothing but carry a few pairs to change into dry ones at night. Another trick if you have nothing else, is to wear ladies’ pantyhose as a base layer. Being totally synthetic they serve the same function and the real thing. For the top half cut out the crotch and toe areas and pull it over your head with your arms through the legs. It does work. Not as well as proper thermals, but if it’s a case of this or nothing…!
The wearing of a base layer may not always be appropriate. In very hot climates, you may find that the base layers thermal properties will cause you to overheat, and you would do better to leave off the base layer and just wear the mid layer. Even tight-fitting underwear may be unsuitable, especially if it is synthetic and washing is not possible. It would be better to go without and allow as much air circulation as possible. We will discuss mid layers in hot climates in the next section.
So, in summary – the Base layer:
- Provides the first layer of warmth
- Removes perspiration from the body keeping the skin dry
- Should be a material that does not ‘retain’ moisture. (No cotton)
- Should dry quickly
- May not be appropriate for hot climates
Mid Layer Garments
Your mid layer is your normal layer of clothing, chosen to suit the environment. Retains heat in cold weather, loses heat in hot weather. No one type suits all situations. In cold climates the mid layer (or thermal layer) is the main layer of clothing designed to conserve heat. Notice it does not create heat, just preserves what your body is producing. If you are not producing body heat, you will not warm up. It does this by trapping the warm air around your body, so you want something that is good at trapping air. Fleece, Down and Wool are great for this. Fleece being cheaper is often the choice now. However, do not be enticed to go for one thick layer however much it looks warm – you want to be able to adjust the efficiency by layering. Layering is discussed in detail in another section. Multiple thin layers, two or three thin fleeces or woollen garments will be more efficient than one thick one.
You want to look for garments that have closures at the wrists and ankles, to assist in trapping air. Some jackets will have a drawstring at waist level and bum level to compartmentalise the jacket trapping warmth.
At the same time, you may want a jacket or trousers that have zips that open up the armpit area and sides of the legs, to be able to vent excess heat without taking the garment off. Double direction (2 way) zips are also desirable, allowing access to the inside without having to open it up completely. Pockets on the outside to store small items are also beneficial.
A tie in point at the wrist to attach you gloves to so they cannot get dropped is great for times you need to remove them.
Look also for garments that have reinforcing at the shoulders, elbows, bum and knee areas. This will protect the garment from wear at these areas.
In hot climates, the mid layer tends to be different. You obviously do not want to be wearing fleece or any garment which conserves heat, you want to get rid of it. So loose flowing garments with lots of venting (mesh panels or zips that can open) is a must. Garments should cover the whole body to protect from the sun. Leave that off-the-shoulder top and crop tops at home or for wearing around the pool. You want protection from the sun and protection from the abrasive wear of your pack on your skin. Many a trip to hot climates has been ruined by a bad case of sunburn.
The fabric for the mid layers in hot climates should be something that will protect from UV radiation and is cool to wear. Cotton is great here as it absorbs moisture holding it and then as it evaporates it creates a cooling effect. There are synthetic micro fibres on the market which also do this, and they are a really great advancement in clothing technology. The great thing about the micro fibres is that they work in hot and cold climates, so you can use the same garment for both.
On the specialised and personal preference side – some ladies like to walk in long ‘trekking skirts’, especially in warmer climates. These allow plenty of airflow, and in areas with little natural screening such as bush or rocks, they provide modesty when going to the toilet. Some men even swear by them.
So, in summary – the Mid layer:
- In cold climates traps heat around the body by reducing air circulation.
- In hot climates, protects from the suns radiation, but allows air to circulate.
- Is your main clothing layer, so should be chosen to suit the environment and task.
- Should be designed with the useful features you need: Pockets, closures, 2-way zips, vents etc. as needed or preferred.
Outer Shell Garments
Your outer shell garments are the primary protection against the environment. This could be different on every trip, so think carefully about what will suit the trip best. In all environments it should protect against wind and precipitation (rain, hail, sleet, snow etc.)
Your shell should also be a working tool. Pockets to carry things you may need without stopping to rummage in you pack, protection from thick vegetation and possibly depending on the trip, high visibility or camouflage in the surroundings.
Shell garments ideally should also have zip zips to vent heat from the garment even in rainy weather. This is especially important in hot climates, but you may still want mesh inserts to keep flying things out. Shell trousers should also be able to be vented, and if you may need to change during the day, having ‘boot zips’ allows you to zip open the lower leg to put footwear on or take them off without removing trousers.
Many people find salopettes extremely useful, especially the non-insulated variety. The insulated ski type is fine for cold weather, but in warmer climates they will be too hot so look for a pair that does not have the insulating layer. Salopettes look like dungarees, with a high bum area and bib in front held up by braces. They are very useful as they protect the body higher up then normal trousers, (great in thick vegetation and snow) but allow one to forgo the jacket unless necessary as they keep the lower body and internal organs of the abdomen protected.
In hot climates you may want to in addition to the waterproof wind proof shell, include a breathable flowing shell to help reduce direct sun contact. An oversized long-sleeved cotton shirt is an example. This can be worn over the mid layer and left loose to allow air circulation.
Your shell garments include things like your boots, hats, gloves and scarves.
So, in summary – the Outer Shell layer:
- Protects from wind and precipitation
- Provides some extra warmth by trapping air
- Protects from the suns radiation
- Protects from the harshness of the physical environment
- Should have pockets to store small items
- Should have venting zips to allow excess heat out
Depending on the conditions, you may need all three layers of gloves (base, mid & shell) however this will only be in the most extreme conditions.
In most cases a single Mid layer glove is fine, with possibly an outer waterproof shell. Gloves are available that combine Mid and Shell into one pair, and these are fine so long as you do not need fine dexterity, as they tend to be bulky.
Two thinner pairs are preferable in wet climates as you can wear one pair, whilst drying the other pair inside your jacket.
Lightweight cotton gloves for very hot climates are also useful to prevent sunburn, but also to protect from surfaces which can get very hot. It is quite possible to get a nasty burn from very hot rocks or metal you may touch in desert type environments, so a basic pair of gardening gloves works fine for this.
The same principles of the three layers of base, mid and shell apply, so even if you are only needing one layer, use the principles of fabric selection we discussed before and in the ‘Layering System’ topic.
The choice between gloves or mitts is always one that has as many opinions as there are people on the trip. Essentially mitts have the advantage over gloves in that they conserve heat better as the fingers are next to each other in the mitt. However, they are no good if you need dexterity to cook, tie knots etc. There are gloves with cut off fingers and a mitt section which folds over the bear finger part which tries to resolve this problem, and so long as the temperatures are not so cold that frost nip is a possibility, they work. In very cold conditions it will be better to have normal gloves with an over mitt on top which can be removed for fine tasks.
Again, what you wear on your head will depend on the environment. In hot climates you want something that will keep the sun off. An open or closed topped peak hat is not the answer. You ideally want something with a full brim to keep the sun off the whole head and neck. Something more like a cricket hat, but of course such a wide brim gets in the way of the top of the backpack if you are carrying one. In windy conditions a stiff brim will be needed as the soft brim variety tend to blow about too much. Make sure it has a drawstring under the chin to stop it blowing away, and even then, tie a thin piece of accessory cord to the hat and clip it to your pack just in case. A large scarf used to wrap around the head and neck is very useful as well.
In cold conditions you will want to make sure your headwear is a thermal layer to stop the heat loss from the head which is considerable. Wool or Thinsulate are ideal for this. Have a separate waterproof layer of buy a Thinsulate hat with a waterproof layer as part of the one hat. A good ridged peak to keep rain out the face is needed. Having a second woollen or Thinsulate cap or beanie, is useful for evenings and sleeping.
Socks are again one of those personal preferences and there are many myths abounding about what to wear.
Just like we described in the base/mid layer sections, socks should: wick moisture away from the feet to keep them dry and provide cushioning from the impact of walking all day.
Think of a raw tomato. You can rub it on your hand for quite a while without any damage to the tomatoes skin but soak it in warm water for 10 minutes then on the first rub of its skin, the skin breaks away. This is exactly what is happening when you get blisters. The most important anti blister thing you can do is keep your feet dry. The two-sock principle works in hot and cold climates. The first layer is a very thin synthetic layer designed to wick away the moisture, and the second thicker layer provides cushioning. We discuss foot care in detail in the H&S section of this course. If you already have your boots, and they simply will not fit two pairs of socks, use ladies’ short stockings (Hose). Being extremely thin they will not bulk up the boot space but will still act as the wicking layer for your feet.
Remember that when buying footwear, consider that you will probably have two pairs of socks on, so wear the sock combination you prefer when trying them on in the store.
Avoid socks which have seams especially in either the heel area or front of toes. These ‘lumps’ in the sock cause extra pressure, creating problems. Look for socks which have no seams at all.
In very wet conditions, it is possible to get vapour barrier socks, which are the shell garments of the feet. As these generally are made of a waterproof non-breathable fabric, you will still get condensation build up inside the sock, so it is important to stop every few hours and dry your feet and the vapour barrier socks out.
In the outdoors especially high up, the radiation from the sun is more intense due to a lack of pollution and or less atmospheric air it needs to pass through, so protection for your eyes is critical. Permanent damage can be caused on just a couple of days from exposure to the glare at altitude, on snow, light sand and water reflection. Your eyes only have one layer of defence – your sunglasses.
Those cheap pair you bought at the local supermarket will not provide the protection you need, even if they seem a very dark shade. It is not the darkness of the lenses which protects your eyes, but the amount of radiation and light they cut out.
Sunglasses should, especially at high altitudes and in high glare situations, be UV protected and Polarised.
The UV protection is the first thing to look for. UV protection is rated from 0 – 4, with 4 having the most protection. The best sunglasses will block 100% of UV-A, UV-B and harmful blue light. In high glare like snow-scapes and white sand, a rating of 4 is a must.
Polarising lenses reduce the amount of light they let in. Again, this is not indicated by the darkness of the lenses, but how they filter the visible light. Be careful though with polarising lenses as in some motor vehicles you may find you cannot read the digital instruments. This also happens with some digital equipment that has digital displays as these displays are often polarised themselves and the double polarisation mean you see nothing.
The sunglasses should also be shatterproof. Manufacturers can now make almost indestructible lenses, so make sure they will not break if you accidently sit on them.
Go for wrap around lenses to reduce the amount of glare coming into the eye from the sides. For extreme conditions you may wish to look for goggles that can either fit over your regular sunglasses or are sunglasses in their own right.
Photochromatic lenses which change shade in different light conditions are fine for general use, but in extreme conditions they do not provide enough protection. Have normal sunglasses as well.
Oh – and use a neck retainer. They are no good to you if they get blown away or you drop them off a cliff when looking over the edge.
Anatomy of a Layering System
What is it?
Layering has become the standard for outdoor clothing over the last few years. There is nothing complicated about it, it is simply using a thin layer of garments, as opposed to a few thick layers, with each layer specifically designed to perform in a certain way to allow for changes in conditions.
Let’s say you are on a trek and it is quite cold first thing in the morning, you have on your normal clothes and a thick jacket to keep you warm. Although it is still cold, as you start walking you begin to overheat. By removing your thick jacket, you now find you are too cold again. If you had on a few thin layers you could peel off one at a time till you reached the ideal temperature.
Multiple layers are better at trapping warm air against your skin as well. But layering is not just about lots of layers. It is about what those layers consist of.
In broad terms, the layering system consists of three layers:
- A Base Layer
- A Mid or Thermal Layer
- An Outer or Shell Layer
The Base Layer
This layer is primarily used to keep the skin dry, by wicking (mopping) up the sweat as it forms and repelling it outwards away from the body. Your body heat drives the moisture outwards.
In hot climates you will not want to use this layer as the moisture on the skin acts as a coolant as it evaporates, so you will want moist skin with air blowing over it which evaporates the moisture and causes a cooling effect.
However, in cold climates, you want the base layer to remove the moisture as soon as it forms so as not to cause this cooling effect.
Base layers can be worn alone if the conditions are not too cold and they help protect your other layers from becoming too damp.
A few points about base layers:
- Typically made from synthetic fibre, merino wool or silk. They need to be made from a fabric which does not ‘hold’ moisture, so cotton for example is a poor base layer.
- Synthetics and silk are very lightweight and wick moisture very well.
- They need to be skin tight to work correctly. If they are loose, then they will not be able to wick moisture effectively.
The Mid or Thermal Layer
This is the layer which keeps you warm. It traps air around you so keeping you in a warm air cocoon. Generally, this is a fleece or wool layer. Two or three thin layers are better than one thick layer so that you can regulate how much you need. The thermal layer is usually not water or wind proof. This is effect is ideal, as it will allow the thermal layer to breath much better than other types of thermal layer which are water or windproof/resistant. Some modern ‘soft shell’ thermal layers are water resistant and windproof, and are great for some situations, but if you must have clothing that can adapt easily to many different conditions, rather go for the basic layer which is not windproof.
A few points about mid layers:
- Typically made from synthetic fleece, down or wool – also should not ‘hold’ moisture as you want the moisture your base layer has repelled from the body to travel through the mid layer into the air to keep the mid layer dry.
- Synthetic fabrics also retain a lot of heat even if wet/damp, so are much better than cotton as an example which retains moisture.
- Down holds moisture so think carefully before deciding on down as a mid-layer if you are going to wet environments.
- Two or three thin layers are better than one thick layer.
The Outer or Shell Layer
This is the shell which protects you against the wind and rain. It also protects against the hard environment such as plants and abrasion.
Your outer or shell layer should always be fully waterproof and windproof. It also by its nature will provide a trap for the warm air inside the garment.
Something to remember with waterproof garments is that they will stop moisture getting out as well as in, so condensation build up inside can cause discomfort. To combat this, manufacturers have developed waterproof breathable fabrics, (see the special article on these), as well as garments which have zipped openings to ‘vent’ the moist air out of the jacket. It becomes a balancing compromise as to whether the moisture build up is more of a problem then losing heat through the vents, especially in freezing conditions.
A few points about outer layers:
- Must be fully waterproof and windproof
- Waterproof breathable fabrics will still sweat inside and are not 100% effective but are much better than non-breathable fabrics.
Does this Apply in Hot Climates?
The principle of layering does generally apply to hot and cold climates, it is just the actual fabrics which change.
In very hot climates you will still find in many places that the nights get cold, so you will need to layer accordingly. The normal synthetic base layer as described before can still be used and it will keep you dry, but you will lose out on the cooling effect of moisture evaporating off the skin.
In hot climates you will want clothing which is loose fitting and allows lots of air to circulate through the layers. You do not want to trap the air like you do in cold temperatures.
Layering still works but change the layers to cottons which retain some of the moisture perspired and as that evaporates creates a cooling action.
The Base Layer
- Cotton or synthetics are fine. Keep them loose fitting so that air can circulate.
- Try to stay with light colours that reflect heat. Dark colours absorb heat.
- Again, stick to cottons.
- Loose fitting with long sleeves to protect the arms from direct sunlight.
- Mid layers with venting mesh panels helps to dissipate body heat.
- For wet times, yes it can get wet, the same shell as for cold climates is fine.
- Additional shells to keep direct sunlight off helps – a simple umbrella.
What Clothing Does This Apply To?
It applies to everything, not just the usual ‘tops & bottoms’, it applies to your hands, feet and head – in cold climates. In hot climates you will adapt the system to allow for free flow of air but reduce as much direct sun contact as possible. Create shade with your layering system but allow airflow. Think of people that live in deserts. They wear long flowing, loose clothing covering their whole body. It keeps the sun off but allows air to circulate.
Waterproof Breathable Fabrics
Waterproof but Breathable garments are often hailed as the best fabrics there are for outdoor clothing. “We can wear them all day in the rain, yet we will stay dry inside”. This is the first myth users will discover when they start using them. Waterproof Breathable Fabrics are one of the most miss-understood bits of gear we use. This short summary of a highly technical subject will try to assist you to understand them better.
Waterproof Breathable Fabrics (WBF) fall into 2 main categories:
Each of these can be either MICROPOROUS (millions of little holes smaller than a drop of water but larger than a molecule of water vapour) or HYDROPHYLLIC (A totally impervious layer that breathes via ‘osmotic potential’ by chemically attracting and dis-assembling the vapour molecule and then conveying it to the other side – much like the cells in our body do).
Performance of either category is measured in 2 main areas.
Breathability or Moisture Vapour Transmission
Breathability or how much moisture can pass through the fabric, is measured in Grams per square meter in 24 hours (g/m2/24hrs) in standard laboratory conditions. This can change radically from sample to sample. Fabrics tested van vary from 2000g/m2/24hrs to 8000g/m2/24hrs.
Microporous fabrics gradually become blocked so reducing efficiency with common detergents, dirt, body oils and body salt crystals. Hydrophylics on the other hand don’t suffer from this drawback, but usually have a lower breathability to start with.
How Waterproof is it or the Hydrostatic Head
This is how much water pressure the fabric can withstand before it starts to leak through. For the outdoor market two meters is acceptable, three metres is the standard’ and over five meters is excellent but not necessary.
Most waterproof breathable fabrics are 100% waterproof, and it is the tape sealing and construction of the garment that causes problems with leakage. The act of sewing alone creates holes for water to get through. Seam sealing is a difficult and expensive process and will regularly be the first-place water gets through.
Breathability is not the most important factor to consider as moisture transfer is dependent on saturation levels which are reached easily – even during an easy day stroll in the park – hence the need for pit zips and additional ventilation. What this means is that if the moisture saturation outside the garment is higher than the level inside – little or no transfer of moisture will occur. (If it’s bucketing down with rain, you will still get condensation build up inside the garment if you are perspiring) This is not the garment ‘leaking’.
Waterproof breathable fabrics work best in dry environments like high altitude areas where the air is very dry.
A semi-liquid coating is applied to the back of a carrier or support fabric. It then bonds to form a layer of about 20-30 microns thick. Many types of coatings are available, and performance can vary from coating to coating. Manufacturer’s battle with applying the coatings – too thin and water gets through, too thick and moisture transfer is reduced. Another problem is some coatings do not adhere properly to the carrier fabric and peel off. Coated fabric technology has improved, and the performance is now nearer to that of membranes and some manufacturers are moving to coated fabrics because the cost of production is cheaper.
Membranes are thin chemical extrusions that resemble ‘cling-wrap’ that are bonded to fabrics that act as carriers and supporters of these delicate membranes.
Membranes, as with coatings present a lot of misinformation and half-truths and Myths. The most common of these is that different testing techniques are used to calculate efficiency rates. Some companies have their own standards and don’t use the common standards. Since the variables are different in each case, confusion is common. So, comparing one efficiency rating with that of another brand may not give an accurate picture – comparing different fabrics from the same brand is fine.
Membranes are bonded to the inside of a carrier fabric. Sometimes a protective layer is then bonded on the other side of the membrane to produce a laminate with the membrane in the middle. This bonding process is referred to as laminating. Laminating is expensive and difficult, one of the reasons why membranes are more expensive than coatings.
The biggest problem of waterproof breathable textiles is getting the coating or membrane to bond successfully with the carrier fabric. The biggest problem facing manufacturers of the garment is getting the seams sealed adequately and the biggest problem facing the retailer is in educating you the consumer about the true pedigree of the product.
The advantages of Hydrophylics are that they don’t suffer from clogging and intra-pore destruction – a fact readily identified by the sailing community.
Bear in mind that as much as 60-80% of the price of high end products is taken up by marketing costs. You are paying for the name, and many lesser known brands are just as good.
This WBF section was adapted from an original article by: Dr Andy Baxter & Dr Stefan Metzker
– Cape Storm Performance Apparel
Special Considerations for Very High Altitude and Extreme Cold
Trekkers considering an adventure in extreme cold (-20 °C) and or and high altitudes (7000m+) might want to think about the following in addition to what has already be covered.
Over dressing is the most common mistake inexperienced people make in extreme conditions.
Mummified in thermals, mid layers, duvet jackets and shell garments they end up in a state of heat exhaustion after only a short while. Cotton clothing and sweating are the two biggest problems. As discussed already cotton absorbs the body’s moisture and when you stop walking, the perspiration that has been absorbed in the cotton freezes, radically reducing the body’s temperature, as heat is drawn away to warm the frozen clothing. When you do start to perspire, stop and remove a layer or two. You want to be in a no perspiration state. When you start to feel cold, stop and put more layers on.
A problem with these conditions is that people tend to wear thick down jackets, which can cause a unique problem. The body’s perspiration is driven outwards, but due to the thickness of the down (or similar fill) the perspiration condenses and freezes before reaching the outside air. This causes a build-up of ice inside the layers of the garment. Having multiple thinner layers allows one to adjust the thickness to get a correct balance of warmth but allowing perspired moisture to escape the garment.
At high altitudes waterproof / breathable laminates become redundant because all the available moisture is frozen anyway, and they can become quite stiff and uncomfortable. Lighter windproof and snow proof nylons make for ideal shells.
Surprisingly for the novice, sunny days on a glacier can be very hot. So, a long-sleeved cotton sweatshirt absorbs sweat and reflects the sun’s radiation.
A number of factors can cause frostbite in these conditions; dehydration, altitude, and cold. Keeping the main body warm is the best way of keeping the extremities warm, as the warm blood will flow to the extremities, but that may not be enough. Mitts, as we discussed in the gloves section, are always warmer than gloves. Do not remove the mitts unless you really must. Learn how to tie knots, put on harnesses and take photographs with them on. A windproof, insulated mitt is ideal. A thin pair of polypropylene gloves will prevent fingers sticking to bare metal when there is no choice and mitts are remove. It is worth insulating any metal equipment you may have to touch with 3 mm foam. The T-bar and handle on your ice axe for examples. Unless you take this precaution, even with a mitt on, heat will be conducted away from the hand to the metal it is holding.
Plastic boots are now normal for cold weather trips. Outers have changed over the years with newer materials less prone to shattering, but the inner boots should be insulated with EVA or Alveolite foam.
Buying separate inner boots allows one to customise your plastic boots, but be careful of bulking up too much that the boot becomes tight fitting. The last thing you want are tight boots as this causes poor circulation and cold feet, which is just as bad as inadequate insulation. In really cold conditions and above 7o00m, insulated gaiters or a full over boot covering the sole of your boot is essential as heat is lost via conduction through to the ground and extra insulation is needed here.
Waterproof vapour barrier non-breathable socks are worn over thin synthetic socks to prevent sweat from reaching the wool socks outer and the inner boots, so keeping those layers dryer (and warmer). Feet are often cold when they are too cramped so the ability to wiggle your toes is essential.
A lot of the body’s heat is lost through the head, making it the fastest way to cool or overheat the body. A thin facemask should be the first layer of protection with a wind proofed fleece Balaclava, and or a waterproof cap. Neoprene facemasks are recommended, as they will not ice-up with frozen breath like fleece will.
Remember that sunny days on snow and glaciers can be extremely hot so prepare for heat as well as cold. If you will be using oxygen, practice your clothing combinations at home first to see what works with the oxygen apparatus.
Select clothing based on the expected environment you are going to. Hot, Cold, Wet etc. Just the clothing out your closet probably will not do an adequate job.
Whatever you take should be easy to maintain. Quick drying, Rugged fabric to resist damage, Non-iron, and preferably colours that do not show the dirt easily. Some fabrics have treatments which help resist the build-up of bacteria, so these are good if you cannot wash frequently.
All clothing should be multi-purpose if possible. Zip off long trousers as an example.
Do not carry a new set of clothing for every day. Depending on the destination you are going to, two sets is usually enough except for underwear and socks which three sets should suffice.
Wash clothing as you go at every opportunity you get.
Multiple thin layers are better than thick garments as it allows you to refine the amount you have on to regulate temperature.
Avoid cottons in wet cold environments. Stick to synthetic fibres which dry quickly and hold heat even when wet.
Your clothing on a trek is NOT a fashion statement – choose items that work for your advantage regardless of what they look like.
Wear any new clothing around town at home before the trip to ensure it does not: chaff, irritate, rub, fits properly, does what its meant to etc. – once on the trail it’s too late.