The layering system remains the smartest way to manage thermoregulation in the mountains, whatever the season.
How to dress in the mountains | Layers are the secret
One of the main challenges when doing activities in the mountains is undoubtedly clothing. Temperatures can be highly variable, and there’s a real risk of wearing garments that are sometimes too warm, other times far too light, partly because of the physical effort involved. Layered clothing, colloquially known as “onion dressing”, is the smartest way to manage this thermoregulation: it lets you adjust body comfort by adding or removing garments based on activity level or changing weather conditions.
Even if you don’t wear all three layers at the start, it’s always worth carrying them with you: you can take something off if the temperature rises, but you can’t add a layer you don’t have with you.
How to dress in the mountains | Base layer: managing moisture
The layer closest to the skin has the essential job of wicking away sweat, absorbing excess moisture so the skin doesn’t stay wet. In cold weather, long thermal underwear keeps the skin warm as well as dry: an essential precaution that, in the most extreme cases, prevents the risk of hypothermia.
Technical fabrics (polyester, nylon)
Advantages: quick drying, consistent performance.
Disadvantages: tend to hold odours more than natural fibres.
Natural fibres (merino wool, silk)
Advantages: natural odour management, pleasant against the skin.
Disadvantages: slower drying, generally higher cost.
Differences between materials are often subtle, both in breathability and in how long odours linger: many people simply choose based on personal fabric preference. As for weight, options range from ultralight to heavy: thicker fabrics keep you warmer, but it’s worth remembering that the primary purpose of the base layer remains sweat absorption, not thermal insulation.
Base layer in hot weather
Even in high temperatures, dry skin provides more comfort than wearing the bare minimum: any summer t-shirt can work as a base layer if it absorbs moisture well, while cotton, perfect on a dry, hot day, should be avoided in winter because it retains water that can chill the whole body when it’s cold. Underwear (briefs, boxers, bras) should also contribute to moisture absorption, a detail that matters even when worn under winter thermal underwear.
How to dress in the mountains | Mid layer: the insulation function
The insulating layer traps the heat radiated by the body: the more efficiently it traps that heat, the warmer and more comfortable you’ll feel. Thicker doesn’t always mean warmer: the efficiency of the insulating material matters at least as much as the garment’s thickness.
Polyester fleece
Advantages: retains warmth even when wet, dries quickly, good breathability.
Disadvantages: that same breathability lets wind pass through, dispersing heat unless paired with an outer layer.
Down insulated jacket
Advantages: better weight-to-warmth ratio than any other insulator, easy to compress (efficiency measured in fill power, between 450 and 900); enclosed in a shell, it also offers some resistance to water and wind.
Disadvantages: loses much of its insulating effectiveness when wet.
Synthetic insulated jacket
Advantages: maintains insulating capacity even when wet, suited to rainy conditions.
Disadvantages: compresses less well than down, so bulkier in the pack.
As an alternative to a full shell, a windbreaker with an internal membrane that blocks air can be enough when rain isn’t expected.
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How to dress in the mountains | Outer layer: protection from rain and wind
The outer layer (shell) protects from wind, rain and snow, and is essential in extreme cases like a storm, when if water and wind managed to get through you’d seriously risk hypothermia. Shells fall into four main categories:
Waterproof/breathable shell
Advantages: the most functional option for borderline conditions, often also the most durable.
Disadvantages: the most expensive in the category.
Water-resistant/breathable shell
Advantages: more affordable, suited to drizzly conditions and high activity levels, in tightly woven fabric that blocks light wind and light rain.
Disadvantages: less protective in heavy, prolonged rain.
Softshell
Advantages: emphasises breathability thanks to stretch panels, comfortable for aerobic activity; many models combine light rain resistance, wind protection and light insulation in a single garment.
Disadvantages: doesn’t replace a true waterproof shell on days of heavy rain.
Waterproof/non-breathable shell
Advantages: affordable, suited to rainy days without physical activity (fishing, recreational events).
Disadvantages: doing physical activity while wearing one still ends up soaking the layers underneath with sweat.
How to dress in the mountains | Layering examples
The following examples are designed for someone who doesn’t feel the heat or cold particularly strongly, doing a half-day hike of intermediate difficulty: personal effort level and metabolism remain variables no generic suggestion can replace.
Cold environments
Medium-light polyester underwear (top and bottom), a synthetic-insulated jacket, medium-weight brushed trousers, waterproof/breathable rain jacket and trousers.
Wet, rainy environments with normal temperatures
Long underwear in light polyester, a light fleece jacket, technical hiking trousers, light waterproof and breathable jacket and trousers (with plenty of vents).
Hot environments
Polyester briefs and a short-sleeved synthetic t-shirt, convertible nylon hiking trousers, a light windbreaker.
The choice between these alternatives depends on destination, time of year, sport practised, budget and, why not, personal aesthetic preference.
How to dress in the mountains | The layering system for different sports
Hiking and trekking
The classic three-layer system works almost always: the main variable is fabric weight, to be chosen based on season and altitude.
Ski touring and snowshoeing
Here the system needs to manage two very different phases: the climb, where you sweat intensely and it’s worth lightening the layers, and the descent or breaks, where the body cools quickly and the insulating layer needs to go back on right away. Dressing lightly on the way up, even at the cost of feeling cold for the first few minutes, is almost always the right choice: it avoids excessive sweating and ending up with wet base layers.
Climbing
Freedom of movement for shoulders and arms matters more than fabric weight: stretchy mid layers and light shells are favoured, often sacrificing some insulation for a fit that doesn’t hinder technical movements.
Cross-country skiing
A constant, intense-effort activity: breathability of the base and mid layer matters more than pure insulation, while the outer layer is often reduced to a simple light windbreaker, given the near-continuous heat production.
How to dress in the mountains | Quick guide by temperature
- At 18-20°C: short or long-sleeved technical t-shirt, with a light windbreaker in the pack for altitude changes or wind gusts on ridges.
- At 10°C: long-sleeved base layer, a light fleece as mid layer, and a windproof or softshell jacket, to lighten on the more demanding climbing sections.
- Below 10°C or in strong wind: heavyweight thermal underwear, fleece or insulated jacket as mid layer, and a waterproof/windproof shell as outer layer, essential above 2,000 metres or in the presence of snow.
The same rule always applies: better to have one extra layer in the pack than to be caught without one halfway through the hike.
How to dress in the mountains | How to wash thermal tops and fleece garments
To avoid compromising the breathability of technical fabrics, wash thermal tops and fleece garments at low temperature (30°C), with a small amount of detergent and no fabric softener: the latter leaves a residue on the fibres that reduces the fabric’s ability to wick sweat away from the skin. Avoid bleach and, when possible, dry garments away from direct heat sources.
Once you’ve chosen and bought the right garments, it’s just as important to develop the right feel for using them in every situation: if rain and wind stop, remove the shell; if physical activity isn’t generating enough heat, add a mid layer, and so on. Many people prefer to put on an extra mid or outer layer at every break, simply to avoid the chill and the consequences of having sweated. Choosing mountain technical clothing remains a subjective matter, but it should be done thoughtfully and with awareness.
For a complete overview on building your whole technical wardrobe, from base layer to accessories, we’ve dedicated a broader guide to hiking clothing, with a specific deep dive into choosing trousers and comparing the various jacket models.
How to dress in the mountains | Frequently asked questions
How many layers do you really need in the mountains?
The classic system involves three layers (base, mid, outer), but you don’t need to wear all of them at once: what matters is always having them available in the pack so you can add them as conditions change.
Is cotton okay as a base layer in the mountains?
Only in hot, dry conditions. In winter or with a risk of rain it should be avoided: it retains water instead of wicking it away, and in cold weather this can chill the whole body quickly.
Is down or synthetic insulation better for the mid layer?
Down offers the best weight-to-warmth ratio and compresses better, but loses effectiveness if it gets wet. Synthetic insulation is slightly bulkier but keeps performing even in rainy conditions.
Do you always need an outer shell even in good weather?
It’s always worth carrying one in the pack: mountain weather can change quickly, and without a shell on hand you can’t add protection from wind and rain if conditions suddenly worsen.
What’s the most common mistake when dressing in layers?
Starting off too bundled up. A body that sweats excessively in the first few minutes of a climb soaks the base layers, and that moisture turns into intense cold as soon as you stop or the temperature drops: it’s almost always better to start with a slight chill than to sweat right from the start.
How many layers should you carry in the pack even if you’re not wearing all of them?
Ideally all three should be available even if not worn at the start: you can always remove a layer if the temperature rises, but you can’t add one you don’t have with you.
How to dress in the mountains | Conclusion
The layering system remains the most reliable strategy for handling variable mountain weather, in any season. Knowing the specific function of each layer, the advantages and disadvantages of the available materials, and always carrying the full set even when not wearing it all, lets you adapt quickly to any change in conditions.
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