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Modern base layers have come a long way from the waffle-knit long johns that were wetted out by lunchtime after a few freeze-thaw cycles. From natural temperature-regulating fabrics like Merino wool to synthetic options engineered to wick moisture, today’s base layers are marvels of technology. Our test crew put 50 items through their paces last winter in locations across North America. Testers skied at resorts and in the backcountry, went backpacking and camping, and ran on both snow-packed trails and city paths to bring you this list of the top performers in the category.

At a Glance

• Editor’s Choice: and
• Best Winter Running Top:
• Best Value: and
• Best One-Piece:
• Most Comfortable Base Layer Bottom:
• Best For Frigid Temperatures: and
• Best for Winter Camping:
• Best for Winter Backpacking: and
• How to Buy Base Layers
• How We Test
• Meet Our Testers

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Editor’s Choice

Helly Hansen LIFA Merino Midweight Graphic Crew and Pant

Sizes: XS-XL
Key materials: Merino wool, polypropylene
Comfort rating: 9/10
Breathability rating: 10/10
Warmth rating: 8/10

Pros and Cons
⊕ Two-layer construction ideal for wool-sensitive people
⊕ Excellent moisture management
⊕ Flat seams are chafe-free under other layers
⊗ No thumb holes

Helly Hansen’s two-layer LIFA merino tech, which sandwiches an internal synthetic layer with an external merino layer, allows folks who are wool-sensitive to experience the material’s benefits. The result was a hit among our testers, who uniformly felt that LIFA’s combination of warmth and breathability made this the ultimate base layer for any winter activity where big temperature fluctuations require the need to stay warm and dry.

While testing this set in regions ranging from the Northeast to the Tetons, testers agreed that the LIFA Merino Midweight crew top and bottom provided warmth on lift rides and windy summits but also wicked moisture extremely efficiently. One tester who happened to have it on while digging out her snowed-in van was impressed with how dry she stayed throughout the physical exertion. For folks wanting even more ventilation, HH makes a zip-neck version for quickly dumping heat.

Best Winter Running Top

Janji Rover Merino Hoodie

Sizes: XS-XXL
Key materials: Merino wool, nylon, spandex
Comfort rating: 9/10
Breathability rating: 9/10
Warmth rating: 8/10

Pros and Cons
⊕ Super stretchy and comfortable
⊕ Thumb slits and ponytail hole
⊕ Doesn’t get stinky
⊗ Baggier fit might not be ideal as a ski base layer

Although Janji considers its Rover hoodie to be a midlayer, this incredibly stretchy and comfortable merino-blend top might be the ultimate versatile hooded long-sleeve shirt. Weighing in at 10.6 ounces, the Rover Merino Hoodie is a true midweight base layer for all winter pursuits, but where it excelled the most during our test was as a running top for a wide range of conditions. Made mostly from merino wool and nylon with a pinch of spandex for added stretch and ease of movement, the Rover pulls on and off easily and feels weightless during your runs, yet adds just the right amount of warmth on cooler mornings and dumps heat effortlessly as your motor gets going.

Testers appreciated thoughtful features including the wide and stretchy thumb slits on the sleeves, a ponytail hole on the snug hood, and a small zipper pocket on the lower hem for stashing coffee money or a house key. I found it to be a fantastic addition to my winter running kit, and I especially appreciated the fact that it literally never got stinky. It’s become my go-to fall and winter running top.

Best Value

REI Co-op Merino 185 Long-Sleeve Half-Zip Base Layer Top and Bottom

Sizes: XS-XL
Key materials: Merino wool
Comfort rating: 10/10
Breathability rating: 8/10
Warmth rating: 7/10

Pros and Cons
⊕ Well-priced base layer staple
⊕ Super soft next to skin
⊕ Built-in SPF 30 sun protection
⊗ Runs big

Anyone shopping for a high-quality merino base layer for skiing that won’t break the bank should seriously consider REI’s lineup. Made with 100-percent ultrafine 185-gram merino wool, this layer provides warmth and next-to-skin comfort without any itchiness or chafing. Flat seams and underarm and crotch gussets to enhance your comfort and range of movement, while the super stretchy waistband is low profile beneath ski pants. (The top is available as a crew neck or a half-zip depending on your personal preference.)

Our testers wore this at resorts as well as on winter hikes and snowshoe excursions, and felt that it got the job done, albeit without any bells and whistles like thumb holes or built-in UPF protection. This would be a good choice for someone with basic long underwear needs who want a quality option that isn’t flashy or fancy,” said one Durango, CO-based tester who wore it in a range of conditions last winter. “I was surprised by how soft the material was. I didn’t notice or feel it while skiing, hiking, or cross-country skiing. After a big sweat, it dried before the chill set in.”

Best One-Piece

Wild Rye Olivia Onesie

Sizes: 0-18
Key materials: Merino wool
Comfort rating: 9/10
Breathability rating: 8/10
Warmth rating: 8/10

Pros and Cons
⊕ Flattering shape
⊕ Boot-top length
⊕ Easy rear zipper for nature breaks
⊗ Runs big

Testers raved about this onesie. A couple of them even admitted to wearing it nearly 24/7 while working from home, going on dog walks, ski touring, and resort skiing. The 100-percent merino wool onesie is butter-soft next to skin, but what sets it apart from other one-piece options are a few thoughtful design components.

Testers loved the soft, wide waistband; it helped keep our ladies from feeling like shapeless blobs while wearing it. Wild Rye put a lot of thought into the rear zip for convenient bathroom access while out in the wild: One tester who wore the onesie beneath a drop-seat bib was happy to report that the interface between the two worked flawlessly. Our lady skiers also appreciated the ¾ boot-top length on the legs and the high-zip neck for added warmth and wind protection. The snug-fitting hood slips easily beneath a helmet, too.

“So warm and cool at the same time,” said one tester. “The lightweight wool is just right for changing conditions, and the hood and high-zip neck keep you snuggly warm when the chill sets in.”

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• ParaGlide bindings feature 2 roller buckles and toe stops that make placing your feet and securing and removing straps simple and intuitive—even while wearing gloves
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• Add-on modular flotation tails (not included) accommodate heavier loads, or allow you to go from packed snow to deep powder with a single pair of snowshoes
• Max recommended load with tails (not included): 250 lbs.

Most Comfortable Base Layer Bottom

Lé Bent Sentinel Midweight Waffle-Knit Bottom

Sizes: XS-L
Key materials: Nuyarn Merino Wool Blend with Bamboo
Comfort rating: 10/10
Breathability rating: 8/10
Warmth rating: 9/10

Pros and Cons
⊕ Great loft and breathability
⊕ Super warm
⊕ Stretchy and comfortable
⊗ Pricey for base layer bottom

Lé Bent waffle-knit leggings use the brand’s tried-and-tested Nuyarn construction, which means the wool fibers are spun around a bamboo filament, rather than coiled, as with traditional merino. The result is more surface area to soak up and diffuse moisture, which leads to a garment with more loft, better temperature regulation, durability, and superior breathability.

Our testers raved about these bottoms, with one Vermont skier admitting that they kept her as warm on the coldest days as her trusty pair of down-insulated crops. “A bit bulky,” she commented, “but worth it for the warmth.”

Classified as midweight, the Sentinel uses a waffle-knit design to reduce the weight without sacrificing the performance. The full-length tight is a bit of splurge for a base layer bottom, but testers argued that it’s a luxury purchase with best-in-class thermoregulation. In other words, you get what you pay for. “OBSESSED with this baselayer,” said our 5-foot, 6-inch tester. “I toured in it and never got too hot. My butt never got cold at the resort, even on the coldest and wettest days.”

Best For Frigid Temperatures

Patagonia Capilene Thermal Weight Zip Neck and Bottom

Sizes: XXS-XL
Key materials: Polartec Power Grid synthetic fabric
Comfort rating: 9/10
Breathability rating: 8/10
Warmth rating: 8/10

Pros and Cons
⊕ Excellent warmth-to-weight ratio
⊕ Breathable in a range of conditions
⊕ Deep chest zipper, thumb loops, and stretchy underarm gussets
⊗ Not offered in a hooded option

Given the heft of Patagonia’s beefiest base layer, we expected it to be less breathable. But while the Capilene Thermal Weight Zip Neck and Bottom is the warmest in the brand’s lineup, our testers were pleasantly surprised by how well this set was able to dump heat, wick sweat, and keep them dry and comfortable throughout a large range of conditions.

Patagonia uses Polartec Power Grid, a lofted synthetic technical fleece that layers a wicking fabric next to your skin to soak up moisture with a top layer that easily disperses it. The “grid” design creates air channels that help keep the base layers light and breathable. “This is a wonderful layer and was often my go-to this winter because I knew it could handle many different conditions and would be the most comfortable,” said one tester who wore it in temperatures down to 5 degrees on shifts as a volunteer ski patroller at Grand Targhee.

Testers also appreciated the substantial layer’s versatility, allowing them to not only bundle it beneath many layers for warmth on the coldest days but also wear it under just a light shell on the skin track or other active pursuits, where they said it performed equally well. Another tester just replaced her set after eight years of consistent wear. “The durability is impressive given the breathability,” she said.

Best for Winter Camping

Houdini Long Power Tights

Sizes: XXS-XL
Key materials: Polartec Power Stretch Pro
Comfort rating: 9/10
Breathability rating: 7/10
Warmth rating: 9/10

Pros and Cons
⊕ Warm and cozy
⊕ No inside leg seams
⊗ Waistband could be wider
⊗ Runs a little long

When warmth is of the utmost importance, Houdini’s Power Tight has got you covered. Literally. They’re stretchy, insulating, breathable, and oh-so-cozy—so much so that testers wore them all day then slept in them on winter camping trips in Utah and Colorado.

Made from Polartec Power Stretch Pro, a dual-layer synthetic fabric with four-way stretch that wicks moisture from the skin and disperses it up and out for quick evaporation, the Power Tights were a go-to pick for our testers all winter. The next-to-skin layer feels cozy like fleece, and the outer layer is silky smooth, making it easy to pull on your shell pants. Testers loved that the Houdini Power Tights have no inside leg seams, so chafing is never an issue, but agreed that a wider waistband might be more comfortable when you’re wearing these around the clock.

Testers who skied in the Power Tights said that they’re quite warm, and advised pulling them out on colder, lift-riding ski days. But for winter camping, all agreed that these were a staple and worth every penny. “I wore them camping early spring in Moab and I was so thankful to have them.”

Best for Winter Backpacking

Minus 33 Long-Sleeve Henley and Woolverino Wool Leggings

Sizes: XS-2XL
Key materials: Merino wool, nylon, spandex
Comfort rating: 9/10
Breathability rating: 8/10
Warmth rating: 7/10

Pros and Cons
⊕ Simple design
⊕ Built-in SPF 50 sun protection
⊕ Comfy, wide waistband with a hidden pocket
⊗ Best for moderate temperatures

In addition to performing well during winter backpacking trips to and fro in temperatures ranging from 10 to 60 degrees, our testers loved that these base layers looked and fit like sporty tops and leggings rather than winter long johns, and that they have UPF 50 sun protection built-in. The Woolverino midweight bottoms feature a yoga-style wide waistband with a small stash pocket and a compression-style silhouette. They are made with a blend of merino wool, nylon, and spandex so they will keep their shape even if you wear them hiking all day, sleep in them, and then wear them to breakfast the next day. The Henley top is made from 100-percent merino wool with a regular fit and flatlock stitching so it’s comfortably worn with a backpack and doesn’t bunch up or rub on your shoulders. The three-button front-closure style adds a bit of flair and airflow while the slightly longer sleeves and hemline add to its classy profile.

How To Buy Base Layers

When shopping for base layers, consider how they will perform when you’re out in the wild. First and foremost, are they comfortable? These are your next-to-skin layers so they need to feel good on your body. Are the seams compatible with backpack straps? Does the hem work well with your ski pants? Does the half-zip, button-up, mock neck, or crew neck satisfy your style? Are you looking for something to wear during long days of uphill travel in the backcountry or will you be spending the day riding chair lifts?

Merino wool fibers are naturally odor-resistant, moisture-wicking, and breathable, but generally less durable as synthetic materials. Because synthetics are usually a blend of fabrics, they are popular with those keen on stretchiness and moisture management. It’s better to buy something that is thoughtfully designed and durable rather than something cheaply made that might fail you on the mountain. Beyond the technical details, you may also want to determine if what you are buying is sustainably produced. Most reputable brands have information about their sustainability practices available on their websites.

How We Test

• Number of Testers: 8
• Number of Products Tested: 46
• Coldest Day During Testing: -10 degrees F
• Warmest Day During Testing: 55 degrees F
• Activities: Resort Skiing, Ski Touring, Camping, Snowshoeing, Dog Walking, Nordic Skiing, Running
• Mountain Ranges Tested In: Rockies, Tetons, Adirondacks, Wasatch, San Juans

Meet Our Testers

Understanding that base layer testing can be highly subjective based on personal preference, body type, activity level, and a host of other factors, we assembled a test team of ladies of all different shapes and sizes, living in different mountain regions, who regularly get after it no matter the winter weather. Category manager and SKI Executive Editor Samantha Berman lives and plays in Colorado’s Front Range, where she skis most weekends at the I-70 resorts. Other key testers include a Vermont ski patroller as well as a volunteer ski patroller at Grand Targhee.