The best Thermal Underwear for a cozier winter!

The best Thermal Underwear for a cozier winter!

The colder months can be pretty darn brutal, but sometimes staying bundled up next to the fire isn’t an option. Whether you’re working outside, going for a jog, or exploring snow country, thermal underwear is a must for cold-weather adventures, as it’ll keep you warm and wick away moisture. Here are the best picks to stay toasty on your next outdoor excursion.

1. Smartwool Men’s Merino 150 Base Layer Long Sleeve

The Smartwool Men’s Merino 150 Base Layer Long Sleeve is an all-around workhorse base layer: It fits great, stays in place, wicks while you’re working, and warms when you’re taking a break. What distinguished this top from other base layers in our test, though, was its comfort and fit: We applauded its long sleeve and shirt length, which kept their wrists and backs covered. It managed to fit correctly and look good on different shapes and heights. Unlike many other base layers, it didn’t cling to the shoulders or back muscles. The microweight fabric—made of merino wool yarn spun around a nylon core—was particularly soft and durable compared with the competition. Despite having perhaps the lightest-weight fabric we tested (the “150” in the name means the fabric weighs 150 grams/m2), the Smartwool Merino 150 kept us insulated in every temperature, and was beloved among our weight-conscious traveling and backpacking testers.

2. L.L.Bean Cresta Wool Ultralight 150 Base Layer Long-Sleeve

The merino wool L.L.Bean Cresta Wool Ultralight 150 Base Layer Long-Sleevetop offers almost all the advantages of a pricier wool top (wicking, warming, and odor minimizing) at a synthetic-base-layer price. We liked the stretchiness of the wool and the thumb loop. The Cresta top comes with L.L.Bean’s renowned return policy, which is a 100 percent satisfaction lifetime guarantee. While this shirt is formfitting, it’s not as tailored as the other tops we tried, so it’s not as stylish, but it works well under other layers for when you’re playing hard.

3. Cuddl Duds ClimateSport Long Sleeve Crew


Despite initial skepticism about this department-store brand, we were impressed by the fit and comfort of the Cuddl Duds ClimateSport Long Sleeve Crew. The top was formfitting on bodies of all shapes and sizes, but not so much that it was constricting. we also loved the long shirt length and the wrist-covering length of the sleeves. Super-stretchy, silky-soft fabric kept the shirt from riding up during movement—and made this top among the most comfortable we tried. However, the fabric of this Cuddl Duds top wasn’t as warm as that of other layers, especially when it became moist from rain or sweat. Multiday backpackers and those who did not wash this top after a single wear complained of odor. It’s a good option for nonovernight activities like day hikes or an afternoon of climbing.

4. Trew M’s LS NuYarn Merino Crew

The Trew M’s LS NuYarn Merino Crew base layer is a good pick for active people who want a slightly warmer and much stretchier base layer than the Smartwool top for activities like backcountry skiing and snowboarding, the latter of which was its original design inspiration. This Trew shirt is made of NuYarn, a two-ply yarn that draws merino wool around a thin core of nylon, so it’s more durable than straight wool but feels as soft as 100 percent merino.

Trew’s NuYarn is significantly stretchier than Smartwool’s core-spun yarn because of how the yarn is constructed; as a result, this top is well-suited for activities like scrambling with a pack and doing acrobatic climbing moves. We liked the shirt’s overly long length because our backs weren’t exposed, even when doing dead-hangs.