During the summer hiking season in most locations, you can get away with wearing a hiking shirt that makes sense. As cooler temperatures prevail in Fall, Winter, and Spring you will likely need to wear base layers on your hikes with a softshell jacket, fleece jacket, or another type of jacket on top. You can also wear a base layer under some winter hiking pants. Layering your hiking clothes is essential to keep warm and comfortable. In this guide, you will learn all about the features to consider when choosing your base layers. And, we cover all the best base layers for hiking that you can get right now.
For the best cool weather hiking clothes, check out our complete guide to Fall hiking outfits.
What are base layers and what do they do?
Base layers are the clothes that you wear hiking that sit next to your skin. These layers can include underwear, long underwear, t-shirts, and long sleeve shirts. Some might consider hiking socks a base layer too. The main purpose of hiking base layers is to regulate body temperature and to wick away moisture aka sweat from your body surface. The best high-performance base layers can help to prevent hypothermia and chafing.
What to consider before you buy your base layers
There are a lot of options when it comes to base layers. So, what’s important?
Material and fabrics
This is the most important factor. You want a material that will wick (remove) moisture from your skin.
First, avoid cotton. It doesn’t wick away your sweat and can lead to feeling really cold and even hypothermia.
The most common and best fabrics for base layers are synthetic (polyester, or a blend with nylon, polypropylene, or rayon), merino wool, or a blend of these fabrics.
Polyester is great because it is durable, wicks well, and dries quickly.
Merino wool is a good option because it naturally insulates, is odor resistant, wicks well, and is breathable.
Go for a blend if you want a mix of their benefits.
Weight and insulation
There are three weights to base layers. Lightweight, mid-weight, and heavyweight.
Ultra-lightweight: These base layers are best for cool mornings or evenings during the warmer months of the year.
Lightweight: The best base layer for cool days where temperatures are above 0C or 32F. When it comes to lightweight base layers, synthetic is typically more durable than merino wool.
Mid-weight: The best base layer for cold weather where temperatures are near 0C or 32F.
Heavyweight: The best base layer for extreme cold where temperatures are well below 0C or 32F during the winter or in cold climates.
Odor control
Some synthetics will have a finish applied to help control the odors that come with polyester. Merino wool naturally controls odor.
The fit
Your base layers should fit snugly and hug your skin. This will allow the clothing to do its job of wicking away moisture and keeping your body at an optimal temperature while you hike. A snug fit will also be more comfortable underneath other layers and prevent the base layer from bunching up.
Below you will find the best base layers for hiking (tops and bottoms), in each weight, synthetic vs. merino wool, for both men and women.
Best lightweight base layers
Lightweight base layers with long sleeves are going to be the best option in early Fall or Spring when temperatures are too cold for T-shirts or short-sleeved shirts alone. You also might require this type of base layer in the Summer for early morning hikes before sunrise, or evening hikes after sunset when temperatures are cool.
First, we look at the best lightweight merino wool base layers.
Smartwool Merino 150 Crew Base Layer Long-Sleeve Top (MEN|WOMEN)
This is a versatile base layer that you can wear for much of the year in cool temperatures above freezing.
- 87% Merino Wool
- 13% Nylon core fiber for durability
- Breathable, soft, lightweight
- Wicks sweat away naturally
- Natural odor resistance
- Flatlock seams reduce chafing
- Raglan sleeve design (no shoulders, snug fit)
Smartwool Merino 150 Long Underwear Bottoms (MEN|WOMEN)
The features and specifications for these bottoms are exactly the same as the base layer top.
Okay, now let’s look at the best synthetic base layer options.
REI Co-op Lightweight Base Layer Long-Sleeve (MEN|WOMEN)
This synthetic base layer will keep you warm and wick away sweat as required.
- 92% polyester, 8% spandex
- Super soft fabric
- 4-way stretch
- Underarm gussets add flexibility
- Flat seam construction
- The lower back hem keeps the shirt tucked in
- UPF 50+ sun protection
REI Co-op Lightweight Base Layer Bottoms (MEN|WOMEN)
Again, this synthetic bottom layer has the same features and specifications as the REI top.
Best mid-weight base layers
Mid-weight base layers are the best choice for cold weather that is near 0C and 32F. So, for example this could be a very cool Fall day or a milder Winter day.
Smartwool Merino 250 Base Layer Quarter-Zip Top (MEN|WOMEN)
We rate the Smartwool Merino 250 base layer tops and bottoms as the best choice overall for cold weather hikes.
- Breathable soft fabric is 100% merino wool
- 10″ (25 cm) front zipper for extra ventilation
- Shoulder panels mean no top shoulder seams (comfort, no rubbing)
- Flatlock seams to reduce chafing
- Wicks sweat away naturally
- Natural odor resistance
Smartwool Merino 250 Base Layer Bottoms (MEN|WOMEN)
These are the matching bottoms to the Smartwool Merino 250 base layer top, and also our top pick for colder weather and snow hikes.
- Interlock-knit merino wool enhances comfort and thermoregulation
- Breathable
- Natural odor-resistance
- Merino-covered elastic waistband
- Flatlock seam construction minimizes rubbing and chafing
- Not itchy, won’t shrink
REI Co-op Merino Mid-weight Base Layer Top (MEN|WOMEN)
If you want merino wool and a lower price go for the REI Co-op merino mid-weight base layers.
- Ultrafine, soft 100% merino wool (not itchy)
- Moisture wicking
- Naturally resists odor
- Flat seam design eliminates chafing
- Underarm gussets for a full range of movement
- Long back hem stays tucked in when you move
- Hugs your body for top performance
REI Co-op Merino Midweight Base Layer Bottoms (MEN|WOMEN)
This is our budget pick for bottoms.
- 200g merino wool
- Flat seams to reduce chafing
- Naturally wicks sweat, and reduces odor
- Wide elastic waist band stays in place and feels great under other layers
- Hugs the body for superb performance
Okay, now let’s look at the synthetic options for mid-weight base layers
Patagonia Capilene Mid-weight Base Layer Bottoms (MEN|WOMEN)
- 100% recycled polyester
- Soft comfortable waistband
- The diamond grid pattern is warm on skin, wicks moisture, and dries fast
- Odor control
- Fairtrade certified sewn
- Gusseted crotch
- Flatlock seam construction
Check Patagonia website (men’s) | women’s
REI Co-op Midweight Base Layer Bottoms (MEN|WOMEN)
- Bluesign approved soft polyester
- Flat seams prevent chafing
- 4-way stretch material comfortable and athletic
- Wicks moisture and dries quickly
- UPF 50+ sun protection
Best heavyweight base layers
These are the best base layers for extreme cold weather conditions and winter hiking.
First, the best merino wool heavyweight base layers.
Icebreaker 260 Tech Crew Base Layer Top – Men’s
- Soft merino wool is certified to the Responsible Wool Standard (RWS)
- Naturally wicks moisture, dries quickly, and manages odors
- Underarm gussets
- Flatlock stitching prevents chafing
- Forward side seams for extra comfort and mobility
- Offset shoulder seams prevent pack rubbing
- Droptail hem stays tucked in at the back
The women’s version is the Icebreaker 250 Vertex Half-Zip Base Layer Top.
Icebreaker 260 Tech Base Layer Leggings with Fly – Men’s
- 100% merino wool
- Contoured pouch with fly
- Gusseted crotch
- Flatlock seams
- Natural moisture and odor management
The women’s version is the Icebreaker 250 Vertex Base Layer Leggings.
Okay, now for our top picks of the best synthetic heavyweight base layers.
Patagonia Capilene Thermal Weight Crew Top (MEN|WOMEN)
- Warm Polartec Power Grid fabric
- 92% recycled polyester, 8% spandex
- HeiQ Fresh durable odor control
- Offset shoulder seams
- Underarm gussets to improve mobility
- Thumb loops
- Flatlock seam construction
Patagonia Capilene Thermal Weight Bottoms (MEN|WOMEN)
Complete the matching set with this synthetic bottom base layer by Patagonia.
- Also constructed of warm Polartec Power Grid fabric
- Super soft stretchy fabric
- 92% recycled polyester, 8% spandex
- Gusseted crotch for mobility
- Flatlock seams
- Brushed elastic waistband for comfort
- Functional fly
