Keep cozy and warm with the best base layers

Base layers are truly the unsung heroes of outdoor apparel. Although tucked away under layers of fancy Gore-Tex and Primaloft, these hidden soldiers play a critical role in trapping and regulating heat next to your skin while wicking sweat and other moisture to keep you warm and dry. Sometimes referred to as thermal underwear or longjohns, the inner layers take on multiple forms: Merino and other wools, silk, fleece, bamboo, and synthetic blends — basically anything except cotton.

They also come in varying thicknesses depending on the level of activity planned and how cold temperatures might be. Base layers feature differing necks, cuffs, and waistlines with choices including zip-up collars, scoop necks, V necks, button-up tops, elastic waists, leggings or tights-style bottoms, fleece linings, and ribbed or waffle-grid patterning options. Whatever your personal preference, you want high-quality materials and premium technology to prevent you from getting cold. Here is a list of the best base layers to add to your outdoor gear closet this winter.

Base Layer Tops

Outdoor Research Essence and Sequence Duo

This technical base layer by Outdoor Research — which includes the Essence long-sleeve for women and the Sequence Duo short-sleeve for men —  is constructed with moisture-wicking Drirelease merino wool and treated with odor-blasting FreshGuard. The industry-leading material uses a mineral-infused technology that blends hydrophobic and hydrophilic fibers to absorb sweat and dissipate heat. Its breathable fabric dries four times faster than regular wool while providing greater thermal insulation.

Castelli Flanders Warm LS

Designed for cyclists, this warm, breathable base layer is ideal for any outdoor pursuit where you’re sweating hard in the cold. With high-loft fleece on the inner lining, it feels silky against your skin while offering top-grade insulation and exceptional moisture-management. The performance layer fits snugly, gliding over your shoulders and settling into place as you stretch out your arms. It has full mesh armpits to provide extra ventilation and flat-lock seams to ensure it doesn’t rub or chafe.

Till I Die Performance Top

This series of long-sleeved, performance tops are the perfect base layers to wear under your ski jacket when you’re hitting the slopes. The athletic tops feature moisture-wicking polyester that’s soft to touch, super lightweight, and fully shrink-proof. Best of all, they come in different retro designs with vintage-style graphics like chairlifts, shotskis, Adirondack chairs, and other ski-themed images — pick your favorite one and head to après in style.

TREW Superlight Nuyarn Merino Pocket Tee

For the outdoor adventurers out there who prefer a tee shirt-style base layer, this pocket tee from TREW offers durable fabric and a slender, lightweight design. The 125 Superfine NuYarn material is constructed from high-end Merino wool that’s stretchy, quick-drying, and rugged enough for the toughest excursions. It has a scooped hem, an articulated back arm, and a laminated stretch-woven pocket.

Pact Stretch-Fit Tank

If you’re looking for a light, tank top-style base layer in lieu of a full-sleeved option, this simple cotton top is a fantastic choice. It features stretchy fabric with a comfortable scoop neck and an extra long torso. The thin material offers coverage without any bulk so it’s perfect for layering. What’s more, the sleeveless layer only costs fifteen bucks so it’s a bargain as well.

Base Layer Bottoms

Icebreaker Men’s Oasis Leggings

Woven with 100 percent Merino wool, these high-performance bottoms deliver incredible moisture management and top-grade temperature regulation. They won’t become damp easily, even when you’re working up a serious sweat, and the simultaneous warming and cooling technology does a solid job managing your body temperature.  Their odor-reducing fibers are remarkably fine and, best of all, you can dump them in the washing machine without fear of them shrinking.

Kari Traa Women’s Tikse Pant

These feather-light base layer pants feature super fine, 100 percent merino wool base that provides warmth while allowing ample ventilation if you’re working up a sweat. The four-way stretch fabric is wonderfully breathable and antimicrobial to reduce odor. They have a soft, elastic waist that holds them in place so they don’t slide down while you’re moving and the body-mapped seams add comfort, as well as a stylish design.

Craft Warm Intensity Men’s Pants

Constructed with an ultra-warm, thermal blend of polyamide, polyester, and elastane, these bulk-free pants are cozy and well-built. The material is baby-soft yet super durable with a 3D knit and athletic fit. The anatomically mapped design showcases added insulation in the areas you need it most while leaving the rest air-permeable and highly breathable. The fabric wicks moisture, lifting sweat from your skin and transporting it to the outer portion of the material where it is able to dry quickly.

Flylow Women’s Mountain Joggers

Made with a looser-fitting design, these lightweight terry bottoms provide extra freedom to move around whether you’re jogging, hiking, backpacking, or even running errands around town. The technical pants, which feature a drawstring waist and fitted ankles, are performance-optimized yet styled with a chic, more aesthetically enhanced cut. The material is soft, cool, and moisture-wicking with an airy, ultra-comfortable feel.

Base Layer Sets

Arc’teryx Rho AR

Arc’teryx’s Rho AR top and bottom set features ultra-comfy Polartec Power Stretch made of 90 percent polyester and ten percent elastane. The blend offers stretchiness and flexibility that lets you move around without feeling constricted by tight-fitting gear. Its insulated material is exceptionally moisture-resistant, shedding sweat and odor while offering supreme breathability. A mid-weight set, it’s extremely warm yet lightweight and bulk-free. Arc’teryx includes a flatlock construction with a soft, plush inner material that clings to your body, enhancing the thermal efficiency by staying in constant contact with your skin. The top piece features a laminated chest pocket and zip-up collar to offer ventilation while the bottom piece has a wide waistband and handy thigh pocket. These machine-washable base layers are a great choice for moderate winter outdoor activities where you aren’t working aggressively and need extra thickness to stay warm.

Kora Shola 230

Made with nothing but pure Himalayan yak wool, this impressively soft fabric features integrated UPF 40 sun protection and odor-resistant fibers. The long-sleeved top showcases a long torso and a sleek zippered collar to offer extra ventilation if you start overheating. The bottoms are constructed with a comfy, soft-brushed fabric waistband and diamond-shaped panel in the crotch area for flexible movement. The base layer set is especially notable for its ability to provide coverage throughout a wide range of temperatures, offering top-notch warming when it’s cold and stellar cooling when it’s hot. base layer top.

Fjallraven Bergtagen Woolmesh

This is without a doubt one of the best all-sport base layer sets ever made. The technical top boasts three different styles of knits in one sleek sweater to deliver versatility regardless of what you’re doing. Not only that, it adjusts to varying conditions and activity levels even within one sport, depending on how hard you’re working. With a multifunctional body-mapping design, it boasts a warm, high-loft wool terry over the shoulders, chest, and upper arms while cool ventilating wool mesh covers the sleeves, side panels, and lower torso. Flatlock seams cut down the chafing factor and the cuff, neck, and lower sides are rib-knitted. The Mulesing-free synthetic merino fibers are durable, breathable, and uber-warm, even when damp. The same body-mapping adorns the long john bottoms with mesh around the front and back of the thighs. Rib-knitting covers the lower legs with a loop-structure elastic waistband for comfort.

Patagonia Capilene Thermal

This fantastically cozy thermal onesie is made from Polartec Power Grid — a smooth, static-free material that’s warm, breathable, and ultra moisture-wicking. The snuggly fabric is stretchy and custom-fitting with Polygiene to assist with odor control. It showcases boatloads of anti-chafe features including flatlock seams, offset shoulder seams (to reduce rubbing at the backpack straps), and gusseted areas on the underarms and crotch. The snug hood is thin enough to fit under your helmet, making the garment Patagonia’s warmest polyester base layer and an ideal choice for skiing. Possibly the coolest feature of this one-piece is that it offers easy access without compromising its heat-trapping properties. For example, the suit features a wrap-around waist zipper so you can use the bathroom without completely undressing. Additionally, the men’s version features a functional fly and the women’s a pony-tail exit so ladies can let their locks hang out.