The clothes to wear for trekking The 4-layer system explained by mountain advanced specialists.

How to dress for a hike or trek: the layering system guide.

When it comes to staying dry and at the right temperature when trekking, there's no use in just multiplying the number of layers: you just need to find the right combination of clothes!

The 3- or 4-layer rule is a heat management and humidity regulation technique that involves switching up clothing combinations based on the weather conditions and the intensity of the physical activity.
Joel and Astrid, mountain guides in Chamonix, explain how you can master this must-have technique for outdoor sports.

The 4-layer technique: Overview

Explanatory video
The key principles of heat and humidity management
Understanding the role of each layer
Mastering the layering system in line with the weather conditions and physical activity

Trekking and hiking: The 3- or 4-layer rule

Adapting your outfit to improve heat and humidity management while hiking or trekking.

When you do mountain sports,whether it's summer or winter, you always need to have the right kit to handle three key elements:
- Body heat: Protecting yourself from the cold and avoiding overheating.
- Weather: Rain, wind, snow, and UV rays.
- The intensity of the activity: physical activity increases your body temperature and causes you to sweat more, which can soon become uncomfortable if it isn't wicked away properly, as you may get cold in your wet clothes as the intensity of the activity decreases.

Successfully layering 4 layers thus allows for sweat to be evacuated and wicked away from the body thanks to a breathable layer, for body heat to be retained or distributed through the adaptation of insulating layers, and for you to be prepared for any weather changes thanks to a protective layer.

The role of each layer and the list of clothes you can use for each layer, for a successful multi-day hike.

While people tend more to talk about the "3-layer technique" in the hiking and trekking worlds, we prefer recommending the 4-layer technique. Of course, when you're on an adventure over multiple days, you'll be exposed to a higher chance of weather changes!

That said, remember: you don't always need to set off with 4 layers in your bag! It's important to adapt your kit to the weather conditions, your personal preferences (weight, comfort, etc.), and your body (level of sweat, tolerance of the cold, etc.).

For further details, you can refer to the full kit list that we recommend for trekking, as well as our bivouac checklist.

1- The base layer

ITS ROLE
Closest to the skin, it keeps your body warm and dry, evacuating sweat.

THE PROPERTIES TO LOOK FOR
It has a soft and breathable material, limiting body odour and allowing for comfortable movement.

THE CLOTHES RECOMMENDED
Upper body: Close-fitting T-shirt, in merino wool or synthetic fibres
Lower body: Leggings in merino wool, only for at night or in extreme cold
Hands: Base gloves in merino wool

GOOD TO KNOW
You can refine the choice of Layer 1 based on the thickness and/or weight of the clothing:
- If it'll be warm and/or you're expecting intense activity that will have you sweating a lot: Opt for something short-sleeved, in a thin and lightweight material.
- If it'll be cold and/or you're expecting the activity to be low to moderate intensity: Opt for something with long sleeves and a heavier material.

2- The breathable and insulating mid-layer

3- The insulating mid-layer

ITS ROLE
Used in cooler weather, it keeps heat close to the body by capturing insulating warm air, whilst also letting out any humidity from sweat.

THE PROPERTIES TO LOOK FOR
It's breathable and retains heat, it has a front zip for evacuating humidity in cases of activity that is more intense than expected.

THE CLOTHES RECOMMENDED
Upper body: Warm down jacket or softshell jacket
Lower body: Hiking trousers or softshell trousers in intensely cold conditions (acts as layers 2 and 3)
Hands: Gloves in merino wool, synthetic fibres or leather (acts as layers 2 and 3)

GOOD TO KNOW
Warmth and insulation are two slightly different things, but they complement one another perfectly! Some clothes are designed more to keep close to the body, whilst being breathable (e.g. Fleeces, whilst others are developed more to provide insulation from external cold, with less breathability (e.g. Down jackets). However, be careful, as you don't necessarily need to wear both: It all depends on the weather, your physical activity, and your preferences. Plus, most importantly, you need to consider adapting the layer over the course of the trek.

4- The external protection outer layer (hardshell)

ITS ROLE
It offers effective protection against rain, snow, and wind.

THE PROPERTIES TO LOOK FOR
It's breathable and retains heat, it has a front zip for evacuating humidity in cases of activity that is more intense than expected.

THE CLOTHES RECOMMENDED
Upper body: Parka, waterproof jacket, windbreaker, poncho
Lower body: Hiking waterproof and windbreaker over-trousers
Hands: Waterproof over-gloves

GOOD TO KNOW
The waterproofing of a component is measured in Schmerbers: The higher the measurement, the more waterproof the component is.
However, watch out, because Schmerbers don't reflect the overall waterproofing of a jacket: Water can always get through seams if they're not taped.

The clothes to wear for mountain trekking, based on the weather conditions, and how to adapt them according to the intensity of the activity

For a trek in cold weather, in winter

The list of clothes advised by Joel and Astrid, mountain guides:
Layer 1: Long-sleeved T-shirt in merino wool
Layer 2: Base layer jacket in merino wool and synthetic fibres
Layer 3: Quilted down jacket
Layer 4: Waterproof and windbreaking jacket

Their top tips for adapting layers during a trek in cold weather:
- If the weather is mild and sunny, only wear Layer 1 for the ascent.
- If the weather is cold, wear Layer 2 for the ascent and descent.
- Only wear Layer 3 for the bivouac or during breaks. Downs and quilting aren't great with humidity, so avoid wearing your down jacket in the rain or when you're sweating a lot.
- Wear Layer 4 in wind or rain. You can even wear it when it's warm and/or during an ascent, as long as you open the zips underneath the arms to evacuate any humidity.

For a trek in warm weather, in summer

Joel and Astrid recommend:
Layer 1: Short-sleeved T-shirt in merino wool
Layer 2: Thin down jacket
Layer 2 or 3: Softshell jacket
Layer 4: Waterproof jacket

Their top tips for adapting layers during a trek in warm weather:
- Only wear Layer 1 for the ascent. If you like, you can add the softshell jacket if the wind picks up or you start to get chilly.
- Once again, don't wear the down jacket for the ascent, you'll risk overheating and ending up wet from sweat (and then getting cold once you stop).
- The softshell can be worn as Layer 2 (in warm and windy weather) or as Layer 3 over the down jacket (if you're really cold).
- Wear Layer 4 if it rains and, if you feel like you're starting to sweat, don't forget to open up the ventilation zips under the arms to evacuate any humidity.

Now you know how to dress to stay warm and dry on the mountain trails. All that's left now is to get your backpack ready and pull on your trekking boots!

The Forclaz editorial team

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