What each layer is for
A base layer moves sweat away from your skin. A mid layer traps warm air. A shell blocks wind and rain. That is the whole system. Everything else is a variation on those three jobs.
For temperatures from 0 to 10 degrees Celsius, a typical setup is a 150-weight merino base, a thin fleece or grid hoodie, and a lightweight hardshell. The total weight is around 700 grams, which is less than most people expect.
- Base: 150 to 200 weight merino or synthetic. Never cotton.
- Mid: 100-weight fleece, grid fleece, or a light synthetic puffy.
- Shell: unlined hardshell with pit zips and a hood.
- Extras: beanie, liner gloves, a spare pair of socks.
Start cold
The rule sounds wrong until you try it. Leave the trailhead with only your base layer on in 5-degree weather, and you will be comfortable within 10 minutes. Start warm and you will be sweating by the first switchback.
Sweat is the enemy. A damp base layer loses most of its insulation, and it does not dry quickly in cold air. It is far easier to add a layer at a rest stop than to dry a soaked shirt on a ridge. If you are still cold after 10 minutes, add the fleece; if you are sweating, unzip the shell and slow down.
Manage the climb and the descent differently
On a 400-meter climb, wear the base layer and shell, with the fleece in the pack. The moment you stop, the fleece goes on within 60 seconds, before you cool down. That 60-second window matters more than any fabric technology.
On the way down, add the fleece and keep the shell zipped unless you are working hard. Descents are colder than climbs because you generate less heat and move faster into the wind.
Hands, head and feet
Cold hands end a hike early for a lot of people. Liner gloves plus a windproof mitten cover more conditions than one thick glove. Keep a second pair of liners in a chest pocket so you can swap when the first pair gets damp.
A beanie costs almost nothing and traps a surprising amount of heat. For feet, thin wool socks with a roomy boot work better than thick socks that crowd your toes and cut circulation.
The lunch-stop problem
Stopping for 20 minutes at a windy summit is when people get cold. Put the puffy on before you sit down, sit on your foam pad rather than a rock, and eat something with fat in it. A small square of closed-cell foam is worth carrying for exactly this.
If the stop is longer than 30 minutes, add a warm hat and move into the lee of a ridge or a stand of trees. Wind is the difference between a pleasant break and a shivering one.
