Cold weather can be a real killer for those under-prepared and who find themselves exposed to the elements in sub-zero temperatures.
Armed with a little knowledge and the right clothing/equipment, you can comfortably brave most cold weather conditions on the planet.
British Armed Forces routinely operate in -35C conditions in areas such as Norway and Estonia.
Here is my advice on how to keep warm during the winter snap this season:
First and foremost, it is all about preparation ... be prepared if you're expecting to find yourself in a cold weather situation.
Wear clothing in a layered system. Three layers in fact: the base layer, insulating layer and outer layer.
The base layer is designed to wick moisture away from the skin and to keep you dry. Merino wool is your best option.
Leggings and undergarments are not just for your grandparents - Merino wool really does work - so wear them.
Next layer on top is the insulating layer - a feather down jacket, or wool, is your best option as both help to trap warm air inside.
Then finally an outer layer - a Goretex waterproof jacket to keep out the water and wind is invaluable.
Your extremities will be the first thing to get cold, so wearing mittens is best practice.
If you do not require the dexterity, stay away from individually fingered gloves - as they separate each finger, meaning more surface area is exposed and a chance for fingers to get cold.
Wearing wool wristlets help promote circulation to your hands.
Goretex boots are life. They help insulate your feet from the cold and wet. Yes, your feet may sweat in them, but also wear them with a good pair of wool socks to wick away moisture.
Tight boots or shoes cut circulation, so loosen them slightly to aid better circulation to your feet and toes.
Just because it is cold, do not avoid fluids.
Stay hydrated - that rule does not just apply to hot weather - your body still needs water to function correctly and the same goes for food.
Wearing a hat is key and will reduce heat loss from your head.
My favourite piece of non-issued equipment and massively under-rated has to be a shemagh - this can be used as a scarf, face mask and hat.
Keep a flask of hot water at all times, top it up regularly and drink hot brews throughout the day.
Before you commence any arduous activity, reduce the layers as your body begins to produce heat - any excess sweat will freeze and you will become cold.
Wear chap stick to protect your lips from the cold wind.
Do not get wet. Seriously, getting wet is the fastest way to a cold weather injury.
If you fall through ice or become wet, it is important to get yourself dry as quickly as possible.
The cold water will be a shock to your body … do not panic, stay calm and get yourself out of the water immediately.
With help from others, strip off your wet clothes and change into dry clothes ASAP - it really is a team effort.
Shivering is a defence mechanism, so listen to your body and cover up, shivering is a way of your body trying to generate heat via your muscles rapidly twitching.
Failing all of that advice ... your platoon sergeant could have you doing press ups and star jumps to warn you up, or why not tell your Physical Training (PT) instructor ‘I’m cold’.
Julian Perreira served with the Grenadier Guards for more than 14 years and spent many years on operations around the world.
From the jungles of Brunei, to the deserts in Afghanistan and operating in Estonia at -31C.
This is how he kept warm.
How do you keep warm in the cold on exercise or operations? Share your advice in the comments.