How do I layer clothing for cold weather outdoors?

What each layer does, why cotton is the wrong material, and adjusting layers before you get hot or cold rather than after.

Difficulty: beginner
Time: 20 min
Read: 3 min
Safety: warning

Short answer

Three layers: a wicking base against the skin, an insulating mid layer, and a windproof waterproof shell. No cotton anywhere. Set off feeling slightly cold, and take a layer off before you start sweating rather than after.

Layering works because it lets you change how much insulation you carry moment to moment. The single biggest cause of getting cold outdoors is not having too little clothing but getting the clothing wet with your own sweat.

Safety

Getting cold outdoors is dangerous, not merely unpleasant. Hypothermia begins with shivering and clumsiness and progresses to confusion and poor judgement, which means the person affected often cannot recognise it. Wet cotton clothing is a well-documented contributor. If someone becomes shivery, stumbling or unusually quiet, get them out of the wind, into dry layers and moving or sheltered immediately, and give them food and a warm drink.

The three-layer system for outdoor clothing

Step by step

Start with a wicking base layer.Synthetic or merino wool, close-fitting. Its job is to move sweat away from your skin, not to keep you warm. Merino has the advantage of not smelling after several days.
Never wear cotton.Cotton absorbs sweat and rain, loses all insulating value when wet, and dries very slowly, so it holds cold water against your body. This includes jeans and cotton T-shirts.
Add an insulating mid layer.Fleece, a light synthetic or down jacket, or a wool jumper. It traps warm air. Two thinner mid layers give more adjustment than one thick one.
Finish with a windproof waterproof shell.Wind strips heat far faster than still cold air, so a shell is as much about wind as rain. It needs to breathe enough to let sweat vapour out.
Set off feeling slightly cold.You will warm up within about ten minutes of walking. Setting off comfortably warm means being too hot and sweating within a quarter of an hour.
Adjust before you need to.Take a layer off as you start a climb, and put one on the moment you stop. Reacting after you are already soaked in sweat or already chilled is much less effective.
Use vents and zips as fine adjustment.Pit zips, a front zip and rolled sleeves change your temperature without stopping to unpack. This is what they are for.
Cover the head, hands and neck.A hat, gloves and a buff are small, light and make an enormous difference. They are also the easiest things to add and remove for temperature control.
Keep a spare warm layer dry in the pack.In a dry bag, not worn. It is for stopping, for waiting, and for anything going wrong — and it is only useful if it stays dry.
Get down insulation and wet weather right.Down is the warmest for its weight and useless when wet. In persistent British rain, synthetic insulation is the more reliable choice.
Do not forget the legs.Waterproof overtrousers matter far more than people expect. Wet legs in wind lose heat fast, and jeans in the hills are a genuine hazard.

Tips

Set off slightly cold. You will be warm within ten minutes.
No cotton, anywhere, including underwear on a long wet day.
Put a layer on the moment you stop, before you feel cold.

Common mistakes

Wearing everything from the start — You sweat heavily in the first ten minutes, soak the base layer, and then get very cold at the first stop. Layers only work if they are adjusted as you go.
Relying on down in wet conditions — Down loses almost all its insulating value when it gets wet and takes a long time to dry. In persistent rain, synthetic insulation keeps working.

If it doesn't work

Soaked in sweat, then freezing at every stop

Cause: Too many layers while moving — Fix: Strip down before starting a climb and put layers back on immediately at each stop.

Cold despite lots of clothing

Cause: Wet layers, or no windproof shell — Fix: Change into a dry layer and add a windproof outer; wind cuts through insulation quickly.

Hands and feet cold while the body is warm

Cause: The body prioritises the core — Fix: Add core insulation and a hat — warming the trunk restores circulation to the extremities.

Waterproof jacket feels wet inside

Cause: Condensation from sweat, not leakage — Fix: Open vents, slow down, and remove a mid layer before it soaks.

Questions people ask

Is merino wool worth the money?

It is warm when damp, does not smell, and regulates temperature well — genuinely good for base layers and for multi-day trips. Synthetic base layers wick as well, cost less and are more durable.

How many layers do I need in British winter hills?

Typically a base, one or two mid layers, and a shell, plus a spare insulated jacket in the pack for stops. The number matters less than being able to add and remove them easily.