Cold Is a System, Not a Jacket

Serious cold does not attack dramatically. It removes options quietly, one at a time. The battery that turned the engine yesterday will not today. The zip you can operate with gloves off costs you a finger's worth of dexterity for the next hour. The condensation from cooking becomes frost on the inside of the roof, then wets the sleeping bag, then stops the sleeping bag working. Winter travel is the practice of noticing these chains before they complete.

The vehicle at minus thirty

Diesel gels. Winter grade fuel is treated for the region it is sold in, which is why you buy locally rather than filling in the south and driving north. Additives help; a fuel heater helps more. Carry spare fuel filters, because a waxed filter is the most common cold weather failure and it strands you exactly where you do not want to stop.

Batteries lose around half their cranking capacity at minus twenty-five. Fit the largest battery that fits, keep it charged, and consider an insulated box. An engine block heater run overnight from mains power at a settlement transforms starting, and where there is no mains, a diesel-fired coolant heater does the same on its own fuel.

Everything plastic and rubber becomes brittle. Door seals freeze shut, and forcing them tears them; a silicone treatment before the trip prevents this. Tyres go hard and lose grip, and in the far north studded tyres are not an accessory but the normal fitment. Air pressures fall with temperature, so check them cold, in the morning, at the temperature you will drive in.

Moisture is the enemy

Every litre of water a person exhales, every pan of pasta, every wet glove dried inside becomes frost somewhere in the vehicle. Ventilate deliberately, even when it feels absurd. Cook outside or under an awning where you can. Never dry clothing above a sleeping area. Brush snow off before entering rather than carrying it in to melt.

In the cold, sweat is the enemy. Everything you wear, and every job you do, should be arranged so that you never get wet from the inside.

The same principle governs clothing. Layers exist so that you can shed one before you begin to sweat and add it the moment you stop working. The discipline is to remove a layer while you are still slightly cold, at the start of the job, rather than when you are already damp. Cotton has no place anywhere in the system.

The clothing system, briefly

• Base: merino or synthetic, next to the skin, changed when it is damp rather than when it is dirty.
• Mid: fleece or a light synthetic insulated layer, easy to add and remove.
• Belay layer: a large, warm down or synthetic jacket that goes over everything the moment you stop moving, and comes off before you start again.
• Shell: windproof above all. Wind removes heat far faster than still cold does.
• Extremities: two pairs of gloves at all times, a thin pair for dexterity and a warm pair over them, plus a spare set in a dry bag. Boots rated well below the expected temperature, with room for thick socks and no compression.

Time and daylight

At high latitude in winter you may have four hours of usable light. Every task takes two to three times longer with gloves, in the dark, in the cold, which means a daily distance that would be trivial in summer becomes a full day. Plan half the distance you would plan in summer, arrive at camp two hours before dark, and accept that a mechanical job that takes twenty minutes at home takes an hour and a half at minus thirty.

Sleeping warm

Insulation from below matters more than the bag rating. On snow, that means a closed cell foam mat under an inflatable one, and an R-value total above six. Eat a substantial meal before sleeping, because digestion is a heat source. Take a hot bottle into the bag. Never sleep in the clothing you worked in, however dry it feels.

Judgement

Cold degrades decision-making before it degrades the body, and the first symptom of that is not noticing. Travel with a second person whose job includes watching you, agree that either can call a stop without argument, and build a schedule with slack in it. In winter, the margin is not in the equipment. It is in the hours you did not need to use.

Questions we get asked

Do I need a diesel heater?

For sleeping in a vehicle below about minus ten, yes, or a very good alternative. It runs on the vehicle fuel, uses little electricity and keeps the interior dry as well as warm, which is the more important half of its job.

Petrol or diesel in extreme cold?

Petrol starts more easily at very low temperatures and does not gel. Diesel gives range and is what the region will sell you. Most polar overland travel is done in diesel vehicles with winter fuel, heaters and spare filters.

How cold is too cold to travel?

Below about minus forty everything becomes a specialist undertaking: metal fatigues, tyres crack, and a breakdown is life-threatening within an hour. Most winter travellers set their own limit far above that and travel with a second vehicle when they approach it.