In this article I will be looking at what to wear to ensure you can stay comfortable and functional when the temperature falls. We will examine both the process and conditions that lower body temperature and how to counter these so you can stay out all year in comfort. Its a sad fact that at this time of year many people reduce how much time they spend outdoors due to temperature and weather, and in doing so miss out on much of what the natural world has to offer. Winter is the best time to put many skills to the test, harvest certain resources like basketry materials and offers unique opportunities to track and observe wildlife, and hone winter tree ID skills.


People can, and do live in very extreme environments both wet and dry, cold and hot, and the main thing such people understand better than most  is how to thermo-regulate, (how to control the body’s temperature) effectively in extreme circumstances.

So why do many Brits tend to feel freezing cold going to the supermarket in December, let alone sleeping out whilst other people happily go about their daily lives at far lower temperatures for much of the year, apparently unperturbed?

To answer this we need to understand the processes that warm our bodies and those that make us cold as well as the weather conditions which are more obvious.

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Watching wild life often involves long periods of time outdoors with little movement....... pay attention to boot fit, dont lace too tight or stuff two pairs of socks on in your summer boot, cold toes will result despite extra socks as space to trap air is reduced.

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How Warm Are We?

Our core body temperature needs to be maintained at 37 degrees Celsius (98.6F), and our bodies have processes to cool down and warm up that assist us, but we are far more effective at cooling ourselves down than warming ourselves up. This is a logical result of our having evolved in warm environments for most of our history, only being able to travel to colder extremes with the assistance of technology (clothing, fire etc) in relatively recent times (in the scale 7 million years of hominid evolution).

In brief we can sweat, vasodilate (expand surface blood vessels bringing more blood to be cooled at the skin’s surface), moderate activity, seek shade, drink cold fluids, contact cold surfaces, sit in the breeze and more, to lose heat, but to generate heat our bodies have to burn calories, which are usually a finite resource, whether backpacking by virtue of what you can carry, or in a survival situation.

This logically leads us to a need to preserve what heat we generate so as to limit calorie consumption.

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  How We Lose Heat.

There are 5 processes that remove heat from our bodies.

1-Radiation- Any object that is warmer than its surrounding environment will lose heat to the environment until the temperature of the two has equalised. This is called radiated heat, and if one of the objects is you at 37 degrees C, and Dartmoor at minus 5 air temp, you can see how the environment will try to drag your temperature way below a survivable level.

2-Conduction- Any two objects in contact with one another will equalise temperatures and whichever is more massive will have a greater effect on the temperature of the other.  So if you sit on a large bolder, or the cold ground, it’s bigger than your behind so it won’t warm up much, but you’ll transfer all your heat and get cold. Some materials conduct heat away from you quicker than others, e.g. stone will rob heat faster than wood, in just the same way as a metal spoon will quickly get hot if left in a boiling pot but a wooden one won’t.  So consider what you a sit or lay on, and insulate yourself from cold surfaces like rock or earth with less conductive materials like branches or a foam mat or jacket, even if just stopping for a brief rest.

3-Convection- When your body is surrounded by gas or liquid, it radiates heat and warms the gas or liquid immediately around it. This is why the hairs on our arms stand up to trap air when we are cold. If that liquid or gas surrounding our bodies is moving, our bodies will fight a losing battle trying to warm air or water that’s constantly moving away and being replaced by colder air/water.

4-Evaporation- If the surface of our body becomes wet, the process of the liquid turning to gas cools our skin.  Nice in the summer, and can be used to cool food and drinks too, but potentially deadly in extreme cold.  Therefore perspiration and immersion must be avoided at all costs.

5- Respiration- When we breathe our body heats and humidifies the air we inhale, and we then lose both heat and moisture with each breath we exhale.  At high altitude this can rival sweating for moisture loss, as we breathe deeply and rapidly working hard in thin air. Whilst moisture loss can be reduced by breathing through your nose, heat loss isn’t reduced this way, as we must still exhale the same volume of warm air.

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Human hermal image, note hotspots caused by radiated heat escaping around head and neck.

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Radiation, Conduction and Convection.

External Factors- Cold/Wet/Wind

So in term of external factors affecting our bodies, the three key dangers are cold air temperature, wind, and wet. A combination of any two of these factors can rapidly reduce your body temperature by some or all of the aforementioned processes if you don’t do something about it. It is no coincidence that more people suffer hypothermia between 4 & 10 degrees c than below zero. This is usually down to being ill prepared, as people fail to recognise the risk of wet and wind or cold combining.

The First Layer of Defence- Your Clothes

Clothing can provide as little as 5-10% of our insulation at home in the temperate regions of the globe, with the rest coming from body fat, but when outdoors in cold weather we need to improve on this. It is not our clothing itself that insulates us from the cold, but the air trapped within the clothing. So for warmth we need to trap as much air around us as possible, but it’s essential to avoid overheating or we will begin to sweat.  If we sweat we get one danger factor, wetness, and combined with a cold environment were already in trouble.  Getting very sweaty could prove fatal at worst, and will certainly require a lot of heat (calories) to dry out, which in the process will cool you (evaporation).


So to avoid sweating we have to monitor and amend activity levels carefully, and adjust our insulation accordingly. This can be achieved by wearing multiple thin layers, rather than fewer thick layers as this gives us plenty of scope for adding and removing layers, depending on conditions and activity levels, which enables body temperature to be controlled effectively.


Materials Choices For Outdoor Clothing - Pros and Cons.

Some traditional materials such as wool are known to everyone, whilst modern manufacturers produce a dizzying array of breathable materials from the original Gore-tex to superlight membranes and much more in between.  So what’s best?  The key is to consider your planned activity, are you stalking animals, in which case low noise is important, will you be wearing it around camp fires (polyester and similar plastic based materials melt from sparks) and any other factors you consider relevant such as weight and degree of breathability versus effectiveness of waterproofing.



Pros- Wool remains a favourite with experienced outdoors people because it insulates effectively, still insulates when wet, (all be it less effectively), it’s hard wearing, resistant to sparks and has a natural antimicrobial element that reduces how quickly clothes begin to smell if worn for consecutive days – a major consideration in keeping your pack to a bearable weight when travelling light, or if away for an extended period of time.

Cons- The down side of wool is it is heavy, even more so if wet, and can be very costly, particularly for good base layers and blankets which always command a premium for good reason.  It can also be quite slow to dry if thick.



Not a choice for a cold weather base layer. Cotton absorbs a lot of moisture and is hard to dry so it will hold sweat next to the body and make you cold. Good for cooling down in hot climates for exactly the same reasons but not a smart winter choice.



Pros-Superlight, cheap, available in density and thickness to please all, modern polyester fleeces are durable, warm, quick drying and versatile, and used for both mid and base layers.  Mostly made from recycled plastic bottles they’re fairly ecologically sound too.  There is huge variation in quality of fleece materials used for items on the shelves of outdoor shops.  Look at the densest pile you can find for cutting wind chill as a light jacket, or the shaggy and fluffy looking types for trapping the most air relative to their weight as mid layers. Polyester in various forms is also used for environmental layers made waterproof by the application of membranes or wash in waterproofing, both of which have an effect on breathability.

Cons- Keep polyester away from sparks as they burn through almost instantly, a potential disaster in an outer shell on a wet day.

If you try to wear a polyester base layer for more than a day or two you will soon notice you are becoming the least popular person in camp. However un-smelly you normally are, you will most likely smell like a dead animal in about three days as bacteria loves polyester. This is why a good wool base layer costs the same as 4 regular polyester ones!



Pros- Nylon is tough and durable and is used for environmental layers and rucksacks as well being the material of choice for wet weather motorcycle safety clothing which can handle extreme wind and rain regularly, as well as being super tough. Nylon can be woven tightly to resist water and when wet it absorbs little and dries quickly.  It can have membranes or coatings applied to further improve its water repellence, although like other materials, the addition of these will affect breathability.

Cons- Still melts, though far less easily than polyester.


Traditional Fibres

Many traditional materials are receiving a new lease of life as Environmental Layers due to new manufacturing processes and new proofing products. 

Pros- These materials tend to be more fire resistant than polyester or nylon, and often make less noise.

Cons- Can sometimes be much more costly than modern materials.



Pros- By weight the most effective insulation trapping more air than anything else.........when dry.

Cons- Once wet the feathers clump and stick together and no longer have any volume or loft and therefore no insulating properties at all. Unfortunately its almost impossible to dry a wet down bag in the field, as you need a tumble drier.


Whatever materials you choose for your kit, choose carefully, and remember, keep it clean or breathability will be lost, keep it dry, and stick to multiple thin loose layers.



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Melting snow with radiated heat from a small fire, using a ball of  snow packed onto a stick- aka Finnish Marhsmallow

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A fresh fox track found on a cold walk, I subsequently followed the tracks to the fox who was not far ahead, in the woods next to my house.

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Setting out to track in these conditions promises ample sign to follow but requires a litte forthought to be comfortable all day outside.

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A back wall fire like this one from last year radiates lots of heat to keep you warm even with no sleeping bag overnight in March- but sparks will be a problem for plastic derived modern fibres.

A good mnemonic to remember for cold weather clothing is:


C -Keep yourself and clothes clean

O -Avoid overheating

L- Wear loose multiple layers

D- Stay dry


F- Fit, ensure clothing is adjusted with good seals at wrist and ankles

E-Exercise, move fingers, toes and face muscles to improve circulation

E-Eat- Heat = calories so eat and keep fluid levels up

T-Tight- Make sure boots and clothes have enough space to trap air and are not too tight.

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