Standing at the trailhead unsure what to wear hiking? Dress in layers: a wicking base, an insulating mid layer and a weatherproof shell, all non-cotton. Start slightly cool and adjust as you go.
For the wider picture, start with the hiking guide that this page belongs to.
| Item | Value |
|---|---|
| Heat loss when you are wet | Up to 25 times faster than when dry |
| Layering system (W.I.S.E.) | Four layers: wicking, insulating, shell, extra |
| Fabric to avoid | Cotton, including underwear |
| Starting rule | Start slightly cold (“be bold, start cold”) |
| Snack timing | Small amounts every hour |
These figures come from the Appalachian Mountain Club’s layering guide. Guidance can change, so check the source before you rely on it.
Why fabric matters more than thickness
Your body constantly gives off warmth, and wind, wetness and standing still all speed up heat loss. Moisture can pull heat away from your skin up to 25 times faster when you are wet than when you are dry, according to the Appalachian Mountain Club. So the goal is to stay dry, not simply to pile on clothes.
Outdoor people have a saying: cotton kills. Cotton traps moisture, and as you sweat or get snowed on, that moisture soaks into the fabric and sits on your skin. The club’s advice is to make every layer non-cotton, underwear included.
Here is how the main fabric choices compare:
- Synthetics such as polyester and nylon are good for lightweight, quick-drying wicking.
- Wool regulates temperature naturally, even when damp.
- Down insulation is light and packable, but its warmth drops when it gets wet.
- Synthetic insulation stays warm when damp, which makes it more reliable in mixed or wet climates.
What to wear hiking: the four-layer system for any trail
The club’s W.I.S.E. system gives each layer one job. OutdoorGearLab describes the same idea as four goals that layers achieve together: wicking moisture, trapping in heat, insulating from cold, and blocking wind and weather.
| Layer | Its job | Typical material |
|---|---|---|
| Wicking | Base layer next to your skin | Synthetic or wool |
| Insulating | Mid layer that holds heat | Fleece, wool or a puffy jacket |
| Shell / sheltering | Outer layer against wind and rain | Waterproof and windproof |
| Extra | Backup for emergencies or big temperature drops | Spare layers carried in your pack |
The layer roles above follow the Appalachian Mountain Club’s W.I.S.E. guide, and the layers-as-a-system framing comes from OutdoorGearLab.
For winter outings, the club also lists the essentials beyond the four layers: a warm hat, waterproof gloves, wool socks and insulated boots. Footwear is its own decision, and the comparison of hiking boots vs trail runners covers it in detail.
Wool or synthetic: which base layer should you pick?
The base layer sits closest to your skin, so it collects the most sweat. Its job, says OutdoorGearLab, is to pull moisture away from your skin and spread it through the fabric. It should also fit snugly and keep some insulating properties, and it should never be cotton.
Both main options have real trade-offs:
- Synthetic (polypropylene, polyester) is not itchy, tends to cost less than wool, lasts longer and dries faster. The downside is that it collects body odor fast.
- Wool, mostly merino today, is thin, lightweight and less itchy than traditional wool, and it does not retain stench. It dries more slowly than synthetics but keeps insulating well when wet, and it tears and abrades more easily on rough surfaces.
The same source notes that increasing numbers of outdoor-savvy people now choose wool for their base layer. Two hikers on the 2,181-mile Appalachian Trail in the summer of 2011 each wore a different type, and the wool shirt’s temperature control suited the muggy, sweaty conditions, although it showed holes at the shoulder after many miles.
Weight matters too. Most mountaineers prefer a thin base layer, because overheating during hard effort can be as big a problem as staying warm. Leave the insulation to the layers above, and consider a zip-neck top, which lets you regulate temperature without stopping to shed an outer layer.
Adjusting your outfit for cold, wet and warm days
Cold days
Pack a spare layer for stops, because standing still speeds up heat loss. Keep your hat, waterproof gloves and wool socks within reach, and add the mid layer as soon as you pause. Carry extra layers in your pack so you can add them at breaks or when the weather shifts.
Wet days
Timing is the trick: if snow or rain picks up, add the waterproof shell before your insulation gets wet. Choose synthetic insulation over down if the forecast is mixed or damp. Keep cotton out of the pack altogether, since it holds moisture against you.
Warm and muggy days
The two sources focus mainly on cold and mixed conditions, so treat this section as an application of the same principles. A quick-drying synthetic or a thin wool base layer manages sweat, and an open zip-neck gives substantial extra cooling when you are working hard. If you still feel overheated even in your base layer, slow your pace and take shorter, more frequent breaks for snacks and water.
How do you stay comfortable once you start moving?
Clothing is not a set-and-forget decision. The club’s rule of thumb is be bold, start cold: if you are warm before you hit the trail, you are probably overdressed. Expect to heat up fast once you move.
A simple routine keeps you in the comfort zone:
- Start the walk feeling slightly chilly.
- If you feel hot or start sweating, shed a layer before you soak through.
- Add a layer when you stop for a break, or when the weather shifts.
- Put on the shell before rain or snow soaks your insulation.
Fuel is part of the system. Your body burns calories faster in the cold, so the club suggests eating small amounts every hour rather than saving it all for one big meal. Cold air is also deceptively dehydrating, since you lose moisture through breath and sweat even when you do not feel thirsty.
The club also warns against alcohol outdoors: it may make you feel warm, but it actually lowers your core temperature and increases dehydration. If you are new to the trail, hiking for beginners covers the wider basics beyond clothing.
Frequently asked questions
Is cotton really that bad for hiking?
Show answer
Cotton traps moisture, which then sits on your skin as you sweat or get snowed on. The club’s guidance is that all layers, underwear included, should be non-cotton wicking fibers, and OutdoorGearLab says never to wear cotton as a base layer.
Should I wear wool or synthetic next to my skin?
Show answer
Either works. Synthetics dry faster, cost less and last longer, while wool keeps insulating when wet and resists odor. OutdoorGearLab’s editors prefer wool for most activities, but note that synthetics are more durable.
Should I feel warm at the trailhead?
Show answer
No. If you are warm before you start, you are probably overdressed. Begin slightly chilly, since you will heat up quickly once you are moving, and carry extra layers for breaks.
Is down or synthetic insulation better?
Show answer
It depends on the weather you expect. The club says synthetic fill keeps its warmth when damp and is the more reliable choice in mixed or wet climates, while down gives up its insulation once it gets soaked.
