People often ask what's best to wear when it's really, really cold. This short animation of all my arctic clobber laid out on a parachute gives an idea of just how much you need to have on to stay warm; this lot worked for me when it got to below -60 Celsius, less than -80 Fahrenheit.
Base Layer – Your next to the skin clothing traps a boundary layer of warm air and wicks away sweat, but it also needs to be comfy – there's nothing worse than an itch you can't scratch through 6 inches of clothing; merino wool is good. Really warm socks are a must, I prefer Thorlo mountaineering ones.
Warm Layers – The layers above your base one are there to trap pockets of air that will stay warm. Wool is best, I like the Swedish ones made by Ullfrotte and you can't beat a Norwegian Army jumper over that. The other, super-warm gear I really rate is made by Austrian firm Carinthia. I've worn it making Survive That and teaching SERE in the high Arctic. The jacket and trousers here are their ECIG (extreme cold insulation garment) ones.
Shell Layer – The outer, windproof layer is the key to keeping the warm air trapped near you, not blown away. Braces on trousers help prevent overheating if you're working by venting excess heat, but it's always best to remove some warm layers before work starts too. Sweat kills in the Arctic because it soaks your clothing, and water conducts heat away from you 24 times faster than air. Really warm boots with thick innersoles, like these Baffin Shackletons, stop warmth leaving by conduction to the snow, they're rated to -100 Celsius.
Head Stuff – To protect your head and face, a warm hat – mine's an old Norwegian Air Force one, neck warming 'headover' and then fur round your windproof jacket's hood works really well, plus goggles for when it's very windy; like under a helicopter.
Hand Stuff – If you lose your manual dexterity through the cold it can mean death in the Arctic, so good hand protection is vital. For working I wear Hestra gloves. For snow-machining (skidoo-ing) or where you don't need to use individual fingers, mittens keep your hands warmer. I wear three layers; inner silk flying gloves, wool-pile warm layer mittens, then fur outers - with wrist lanyards to prevent losing them in high winds.
The final layer is for the E & E part of SERE, snow camouflage protects you from hostile detection, 'nuff said. It takes a long time to get dressed.