People new to hiking usually fear the cold and so dress very warmly from the start. Twenty minutes later, as the climb begins, that thick jacket becomes the cause of feeling cold, because sweat has soaked the base layer through.
The three-layer principle solves exactly this. The base layer does the work of moving moisture away from the skin. The mid layer holds warmth. The outer layer blocks wind and rain. The adjusting happens at the mid layer: take it off or put it on before you begin to sweat, not after.
Three layers, and how to choose the fabric
- Base layer: merino wool or a synthetic fabric that moves moisture. Avoid cotton, because cotton holds water and stays cold for a very long time when wet.
- Mid layer: a synthetic fleece, a light insulated jacket or a wool sweater. It is worth having a thin one that stuffs easily into a pack.
- Outer layer: a windproof jacket with a hood; if rain is forecast, choose a waterproof one with vents.
- Feet: wool or synthetic socks, with a spare pair in a waterproof bag.
- Head and hands: a thin hat and a pair of light gloves take up very little room and make a large difference when it is windy.
Adjust for the terrain, because adjusting for how you feel is already too late
Before a climb, take a layer off even if you feel slightly cold. Before a rest stop or a windy section, put one on straight away even if you feel warm. It sounds backwards but it keeps the base layer dry, and a dry base layer is what decides whether you get cold.
On trips in the north we have found the most common mistake is not carrying too few clothes but changing layers at the wrong moment. This is a ZUNGZA observation on damp and misty forest routes.
Rain and mist
In rain the outer layer matters most, and pit zips or a two-way zip keep you from steaming up inside. Mist is harder than rain: it wets you slowly, evenly and quietly, so many people only notice once the mid layer is already damp. If you are walking in thick mist, put the outer layer on from the start.
A few questions you often send us
Is a thin disposable rain poncho enough
Enough for one short shower on easy ground. On a forest path with branches and thorns this type usually tears after a stretch, and then you are both wet and carrying extra rubbish out.
Do I need expensive technical clothing
Not necessarily. The order of priority should be: the right fabric for the base layer, one windproof layer, and one spare pair of dry socks. Those three cost far less than a premium shell worn the wrong way.
Does layering make the pack heavier
Slightly, but not by much, because each thin layer is lighter than an equivalent thick jacket. In return you get many levels of adjustment, which is something one thick jacket cannot give.