Hypothermia is defined as a dangerous drop in body temperature, essentially where it drops below 35 degrees Celsius.
It is classed as a medical emergency and can be caused by things like:
- Falling into cold water
- Being in damp clothes
- Being in cold conditions without appropriate clothing for too long
Now the UK has a pretty mild temperature relative to other parts of the world. So you might not associate hypothermia as being a hiking risk here.
But not only does hypothermia kill hikers all over the UK every single year, it also results in mountain rescue call outs even in summer!
A walker taking on the Welsh 3000s was rescued in Snowdonia (North Wales) at the end of July 2024. And further south than that, early July saw two walkers suffering hypothermia rescued on Dartmoor.
So:
- Don’t make the mistake of thinking the UK isn’t cold enough for hypothermia
- Don’t assume it’s only a risk in winter
However, it is of course a much bigger risk in the winter months. For those of us who like to hike mountains, where the temperatures are lower than sea level by far, winter can bring some brutal temperatures across the UK (particularly in Northern Scotland).
The average winter temperature on the summit of Ben Nevis, for example, is -5 degrees Celsius.
So of course it’s much more of a risk in the winter time.
With that in mind, let’s take a look at spotting the signs and preventing hypothermia.
How to Prevent Hypothermia When Winter Hiking
Hypothermia is much more a risk when you get cold and damp. So there’s two really important things to bear in mind when out hiking mountains (particularly in the winter):
- Having sufficient (and spare) warm layers
- Protection from wet conditions
Your winter hiking kit should include plenty of layers. You’ll likely need a baselayer, mid layer, insulated winter jacket and outer shell. And don’t forget to take spare layers too.
Take an emergency survival blanket or bag as well.
The body loses heat rapidly when cold and wet. So if you end up taking a tumble in the snow and get wet or rain sets in (like it does all the time in the UK) you can find yourself quickly cold.
Synthetic vs Natural Down for Winter Insulated Jackets
When it comes to winter insulated coats, my personal preference is for synthetic insulated jackets. That’s because, despite the fact that natural duck or goose down holds more warmth by weight, the feather down is essentially completely useless when wet. It clumps. And it takes a really long time to dry. So your winter jacket, if you’ve got a down jacket, offers really limited heat at all once wet.
Synthetic insulation is designed to dry faster and still offer some protection even when wet. So personally, I opt for a synthetically insulated jacket for my hiking.
Amazon has tonnes of these from brands like Rab, Berghaus, Mammut and others.
Thermal Baselayers
I always wear baselayers in the winter temperatures. On occasion, I’ve wondered whether it’s overkill – especially at the base of a steep hike when the temperature isn’t that low and I’m walking up an incline and feel warm!
But I never regret the decision to wear them.
There are so many out there and so many different fabrics to choose from. The main debate is generally whether to go with merino wool or a synthetic sweat wicking fabric.
Both have their benefits of course. Merino wool is incredibly warm and naturally wicking too. But it tends to be more expensive than synthetic baselayers.
Personally, I’m a fan of merino wool and although more expensive than synthetic layers, mine have lasted me years.
I wear merino wool baselayer tops and bottoms in the winter. Mountain Warehouse have a really lovely range at not totally unreasonable costs.
Merino Wool Women’s Baselayers
Merino Wool Men’s Baselayers
Outer Shell
Many insulated jackets are water resistant as opposed to waterproof. I always carry a my Mammut Alto Guide waterproof with me as it its water column test rating is 20,000mm, making it highly waterproof fabric. This goes on over the top of my insulted jacket if it starts to rain because being wet and cold at the same time is an absolute hypothermia risk.
Socks, Hat and Gloves
Keep plenty of socks and gloves spare in your bag. Merino wool socks are great and warm. personally I like the Trespass two layered socks below which keep my feet warm and blister free too!
And recently I tested some HeatPerformance heated gloves which will be a staple for me on the mountains this winter.
Of course, a hat is absolutely essential too.
But the important thing with all of these items is having spares in your bag. It’s absolutely essential. Hands, feet and heads can easily get wet. You need to be able to get them dry quickly which means spares!
Emergency Survival Bag
I often say my hiking bag (particularly in winter) is full of things I have to carry around but hope I will never need. A survival bag is one of these things.
It’s probably the cheapest piece of equipment I carry with me but is a potential lifesaver.
For a few quid, having one of these in your bag really is sensible.
If you end up with an injury that means you can’t move when up a mountain, your main task is to stay warm and avoid the onset of hypothermia until help gets to you.
Sitting still in cold temperatures really has the cold setting in, so having access to something like this for absolute emergencies is a no brainer.
Spotting the Signs and Symptoms of Hypothermia
I think even if you take all the right precautions to avoid hypothermia when you are hiking, it’s important to know the signs.
So, hypothermia usually comes with:
- Intense shivering
- Disorientation
- Lethargy
- Poor decision making
- Slipping or stumbling around a lot
If you spot these signs in yourself or someone you are hiking with, they potentially have hypothermia or are at risk of it.
What to do
If you or someone in your hiking group has possible hypothermia, layer up. Add layers wherever possible, drink something and eat.
If they’re wearing any wet clothing, you ideally want to get this swapped for a spare dry one.
We want to avoid dehydration, get some energy on board and hope for an improvement in symptoms.
If symptoms improve after this, then walk yourself off your route the shortest and quickest way possible.
If they don’t improve, call for mountain rescue… and this is where your survival bag will come in handy while you wait!
