How to stay warm in the mountains

Following on from the interest in my post about Ways to keep your hands and feet warm in the mountains I thought I’d write an article with more general tips on how to stay warm in the mountains. In this article I will look in some detail about the systems and strategies for staying warm specifically in the British winter mountain environment.

“Be cool, not hot”

How to stay warm when Scottish winter climbing

Keeping your body temperature at an optimum makes for a more enjoyable day in the hills, improves your physical and mental performance and guards against the serious, and potentially fatal, condition; hypothermia.

Most people know about using a layering system. I’ll look at the layering system in more detail, as well as discussing other principles which are key to staying warm. Including, environmental considerations and the body’s physiological response to exercise and staying warm.


Be Cool, not Hot

First of all, to understand how to stay warm in the mountains, especially the winter environment, it is critical that it is understood that the key to this is not to overheat.

Yes, that’s right, getting too hot is the enemy. This is because when we overheat our body sweats. Moisture next to the skin will conducted heat away from the body 25 times quicker than if dry. Everyone is different and we all sweat to different degrees, at different levels of exertion and ambient temperatures, that is why it is impossible to give a clothing system that works for everyone. However, the principles are the same.

Not only does overheating cause sweating, which makes you cold, it also stresses the body. Steve House and Scott Johnson’s book, Training for the New Alpinism, explains how this is detrimental as the body must put energy into expelling heat, one of these mechanisms being sweating. In essence, we should seek, not to be warm when moving in the mountains, but slightly on the cool side of a comfortable temperature.

The adage ‘be bold, start cold’ is also very true. We quickly warm up when our muscles are moving. If you’re the right temperature before you start moving, you’re wearing too much, so take a layer off.

If sweat is the enemy, then how do we reduce this occurring? There are 3 principles:

  1. Wearing the right amount, and type, of clothing for your body and level of exertion.
  2. Adjust clothing by removing layers and venting.
  3. Moderating the ‘level of exertion’, a.k.a. walking slower.

The final point is often overlooked, but is the quickest and easiest way to stop overheating.

Base layers in Scottish winter


Fabric matters

It is important that the qualities of different fabrics and their suitability for outdoor clothing are understood, before  discussing layering systems.

If the enemy is sweat, then sweat’s co-conspirator is cotton. ‘Cotton kills’ is not an overstatement. In the 1960’s, Dr Lewis Pugh, a British researcher, made the connection between an incident involving multiple hypothermia fatalities and their clothing. They were wearing jeans and cotton shirts.

“If the enemy is sweat, then sweat’s co-conspirator is cotton.”

Although the message about not wearing jeans in the mountains is now widespread, it is surprising the amount of people who can be found wearing cotton T-shirts, leggings and hoodies. When cotton is dry it is not a problem, the problem comes when it gets wet, or damp with sweat. This is because cotton holds moisture next to the skin. Moisture on the skin’s surface sucks warmth from the body, and cotton does this better than any other fabric. Therefore, wearing cotton next to the skin, like with T-shirts, is particular BAD! Read the article, how a dead man’s clothes changed survival advice, in the further reading section.

Even if people don’t understand about why cotton is a terrible choice in the mountains, by the time they get to the winter environment most people do understand that they need to invest in specific outdoor clothing. This clothing isn’t made of cotton, so they are not at risk. Although it’s worth looking at what underwear you are wearing, especially if you get a sweaty lower back. Most underwear is made of cotton or cotton mixes, investing in specific underwear for the outdoors,  will reduce getting a cold lower back.


Down clothing?

Another material which is unsuitable for our cold, wet environment in the UK is down. Down clothing, being specifically made for the outdoors, is often worn in error in the UK. Down is a fantastic insulator in cold, dry climates, but this isn’t the case in the UK. The problem is that if down gets wet then is has no insulating properties, unlike synthetic insulation which will keep you warm even when it’s wet.


Fit matters too

It is important to remember that the layers themselves don’t keep you warm, it is the air which is trapped in, and between, layers which keeps us warm, similar to the effect of double or triple glazed windows. Therefore, if we have a layer that is too small and squishes the air out of the other layers, it could actually mean getting colder than if the layer wasn’t worn. Due to this, we need to be mindful of our layers being the right size, the right shape and how they fit over each other. The only layer which should be close fitting is the layer next to the skin, known as the baselayer.

Conversely, it is also possible for layers to be too big. If a layer is too baggy then a venting affect (see below) occurs and the nice, warm air readily escapes with movement and is replaced with cold air.

“it is the air which is trapped in, and between, layers which keeps us warm, similar to the effect of double or triple glazed windows”

Layer up

Throughout any day in the mountains two variables are constantly changing; the elements and the level of exertion. It gets colder and windier with elevation gain and we exert ourselves more going uphill compared to down. Winter climbers must cope with the most extreme changes in their level of exertion; steep walk-ins to the base of routes, followed by being stationary whilst belaying.

If we wish to avoid sweating, and stay at the optimum temperature, this means that clothing needs to be adaptable, remove sweat away from the skin, known as wicking, and be easy to adjust and vent.

For adaptable clothing, ‘layers’ of clothing have several advantages. Firstly, it means we can remove or add layers to micro-manage body temperature and secondly, layers create the ‘trapping’ of air effect which keeps us warm.


A typical laying system involves:

A baselayer (or thermal) – Can be worn on the legs and upper body. They do the job of removing, or wicking, sweat away from the surface of the skin. The material is either synthetic or wool (often merino), if you don’t get on with one try the other. Most of my base layer tops have zip necks so I can vent easily as I walk.

A couple of mid-layers – There are lots of options here. Layers generally consist of fleece or lightweight synthetic materials. Several mid-layers are often worn or carried.

Hardshell –  waterproof jacket and trousers. The three most common materials favoured in the British hills are Gore-tex, eVent and Paramo.

Belay jacket/emergency layer – A big warm jacket that you only plan to wear when you stop or in an emergency. This layer needs to be big enough to go on over everything. I often buy a size larger to get the right fit. For the British climate synthetic fabrics, rather than down (which doesn’t work if wet), is the most suitable.


Some more points on layers

The most difficult layers to get right are leg layers. This is because once waterproof trousers, harness or crampons are on you’re committed! They really need to be right at the start of the day. Variations on thermal/baselayers, softshell and, when it’s coldest, fleece/powerstretch trousers are options.

If you are a real sweater, or anticipate a tough walk-in before belaying for hours, some people go to the extreme of carrying a spare baselayer top, changing into it on the hill. If this is a bit extreme for you, the alternative I find works well is the following: I walk-in in a baselayer with a softshell/hardshell/windproof according to the weather. It is unavoidable that beneath a rucksack my lower back gets wet from sweat. When I need to add a layer I put a fresh layer on over my damp baselayer but beneath the second layer I’ve walked-in wearing.  If I use a mid-layer like powerstretch fleece I find it is very effective in ‘sucking’ any moisture in the baselayers and dispersing it, making me feel warm and dry very quickly.


Adjusting layers on the go

Adjusting layers by venting can take various forms but generally means loosening clothing to help the body to stay cooler. To remove a layer requires a stop, but venting can be done on the move. This trick for micro-adjusting layers helps to keep the body at the optimum temperature to perform.

Removing your hat or other headwear and stuffing it in a pocket is one of the simplest things to do and will immediately make you feel cooler.

To vent jackets there are several options. Not wearing the hood up, unzipping the main zip, loosening cuffs, or even rolling up cuffs to expose wrists can all help cool the body. Some jackets come with come with specific zips for venting like pit zips.

Layers beneath jackets are easy to vent if they have zips at the neck, and as such I always buy layers which either have a full-length zip or zip at the neck, even down to my baselayers.

As I mentioned earlier, getting the layering system on the legs right can be difficult. One thing that can help is having leg layers which are possible to vent. Some winter trousers come with specific zips for venting. In the UK, as we tend to wear waterproof shell trousers for much of the day, I always make sure I buy ones with ¾ length zips. Having the zips on these trousers end at around the hip means that it is not only possible to get trousers on and off over boots but, more important from a venting perspective, I can unzip them slightly from the hip and thus vent if I’m overheating. I can do this even with a harness on. With full length zips you risk your trousers falling down!

Conversely, reversing any of the above actions will reduce heat lose and will result in staying warmer.


A spanner in the works; it rains in the UK!

Wet Scottish winterApart from sweat, the British hills give us another challenge, in winter they can be both cold and wet. It is not uncommon that it is raining in the carpark, which turns to sleet and then snow with height gain. The wetness of the snow also results in the dampness seeping into gloves, boots and layers.

The wet, cold climate of the UK means that in the British hills we often go out in full waterproof shell layers from the off. If we’re not starting in our shells then we carry them in anticipation that we’ll be wearing them at some point. The alpine system of softshell clothing just isn’t water resistant enough for our climate. It’s not to say that softshell clothing isn’t useful. I use it beneath my waterproofs for double insurance in keeping the rain out!

Ideally, we’d not wear waterproofs if we don’t need them, as even the best waterproofs trap moisture more than not wearing them. This means the enemy – sweat – can return.

There are different types of waterproof, breathable fabric which people can try. The main ones being Gore-tex, eVent and Paramo. Getting the amount of layers beneath waterproofs right is critical so not to overheat, and then knowing how to adjusting clothing by venting (strategies for this I discussed above).

If you’re wearing minimum layers beneath a waterproof shell and are venting but still sweating, then the thing to do is exert yourself less – slow down.


Another consideration: Wind Chill

Although temperatures in the UK rarely get below -10°C, more often than not hovering just below freezing on the summits, they are frequently accompanied with strong winds. Therefore, it may only be -2°C on the summit but with a 55kph wind it could mean it’s -22°C with wind chill.

Wind chill

How to stay warm in the mountains means guarding against wind chill which can be done by wearing a windproof layer. Luckily shell clothing is not only waterproof but it’s also windproof. However, if you feel you’ll overheat in a hardshell, a softshell, or other types of windproof fabrics, might be more comfortable to wear.

Wind chill can affect any exposed skin and sometimes it can feel particularly cold on the ears and face. A hat or buff is good to protect the ears. For the face, putting ski goggles on can increase warmth. Goggles should always be carried in Scottish winter, without them blowing snow can make it impossible to see and is painful. However, lots of people forget that goggles can also be worn to help keep your face warm.


Scottish winter mountaineering food


The fire needs fuel

All the layers in the world won’t keep you warm if your body can’t produce heat. Muscles produce a lot of heat when used, so keeping moving is a good thing to do. However, your muscles need fuel for this. In fact, a body needs a lot of calories just to keep itself warm even without moving much.

Having a substantial meal the evening before going into the hills is essential for your body to have energy available the following day. Eating a good breakfast also helps set your body up for the day. The food taken on the hill therefore tops up and maintains calories available to the body.

“If you’re cold ask yourself, when did I last eat and drink?”

Most of the time I find that people carry more than enough food for the day. The problem is that they don’t eat it. There are many reasons for this; conditions mean that people don’t want to stop, their food isn’t easily accessible, they don’t feel like eating the food they’ve brought with them and it takes effort to stop to eat so they don’t.

To prevent these problems food needs to be accessible, easy to unwrap with gloves on or without packaging, in a snack format, tempting enough to want to eat and short, regular breaks taken to eat. It takes thought and organisation to prepare food which is easy to eat on the hill, anticipating where will be good a place to stop and have snacks stashed in pockets so they can be eaten on the move or at a belay stance. I believe that these things are all more important than exactly what food is taken on the hill.


Remember to hydrate

Staying hydrated is not only important for performance but it’s also key for staying warm. Hydration is critical for the body to turn food into energy. It is essential that you start the day well hydrated, otherwise you will be on the back foot before you’ve even begun. Then, once out, having accessible fluids that you want to drink is important. This could be water in a sports bottle or hot squash in a flask, or both, whatever works for you.

If you’re cold ask yourself, when did I last eat and drink?


Exhaustion is also a factor

Exhaustion means that the body no longer has the energy to continue at a reasonable rate. If the body has no energy to move, then it has little energy to stay warm. Moving slower also means less heat is generated from muscles. When in a group it is important to also think about how others are affected, as they are also likely to get cold as the pace slows.

Being mindful of the effect of tiredness both on yourself, and others in the group, when you make any plans. Get as fit as possible for the winter mountains and make more conservative plans with winter trips. It’s likely that things will take longer and are more physically demanding than in summer. Remember you always have options; turning back and/or resting in a group shelter (see below), are better choices in almost all situations, when someone is becoming exhausted.


Inside an emergency shelter


For Emergencies…

As mentioned above, my layering system always includes an emergency layer or belay jacket. This is a layer I only plan to use when stationary. This layer is an important element of my safety system when in the hills. However, in addition to this, I always carry a group shelter.

“I think a group shelter is more important than a first aid kit for safety in the mountains”

I carry a two-person shelter when carry when climbing. For hillwalking I carry a 4, 6 or 8 person one depending on the size of the group. In fact, I think a group shelter is more important than a first aid kit for safety in the mountains. They are light and can live at the bottom of a pack. Getting in them cuts out the wind chill immediately. In addition, body heat quickly raises the temperature in the shelter. Sometimes you have to get out of the shelter because it gets too hot! Without a doubt group shelters are life savers. They are also a much more pleasant place to have a snack or sort out a blister than in the open on the Cairngorm plateau in winter.


And Finally…

I hope these tips are useful to people. If you have any of your own tips write them in the comments below. And finally, be safe out there folks, be prepared and wrap up warm (but not too warm!)


Want to join me in Scotland this winter?

guided winter Buachaille Etive Mor

Get in touch about a winter guided day or learn skills for the winter here.


Further Reading

Hiking Safety: How a dead man’s clothes changed survival advice

10 tips on how to stay warm in winter by Andy Kirkpatrick

Why Cotton Kills a technical explanation

If you ever need reminding about how important it is to stay warm in the mountains and that our albeit hills of low elevation can be lethal I recommend reading Cairngorm John by John Allen. John is a former team leader of Cairngorm Mountain Rescue, as with all teams, a committed volunteer. It is thought provoking the amount of times hypothermia is a factor, if not the main reason for a tragedy. A sobering number of times bodies of victims were found less than a kilometre away from a car park.


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