10 Best Thermals For Winter 2026 in the United States

The Merino.tech Merino Wool Base Layer Set for men is a strong choice for anyone needing reliable warmth in cold weather. Made from 100% superfine merino wool, this set offers a soft, comfortable fit without the itchiness often found in wool products. It comes in three weights (lightweight, midweight, heavyweight), with this particular midweight version striking a good balance for cold but not extreme conditions. The fabric naturally wicks moisture away and resists odors, helping you stay dry and fresh during physical activity or daily wear.

Its breathable nature also means it helps regulate body temperature, reducing the risk of overheating. The set includes a top, bottoms, and even merino wool hiking socks, adding extra value and enhancing layering options. While it’s machine washable, hand washing and air drying are recommended to maintain durability over time. This base layer fits well as an all-around winter thermal, ideal for hiking, skiing, or everyday outdoor use in cold climates.

One possible drawback is the need for gentle care to keep the wool in good shape, which might be a bit more effort than synthetic alternatives. But for those prioritizing natural fibers, comfort, and moisture control, this set delivers excellent performance.

The SmartWool Womens Classic Thermal Merino Base Layer Crew is designed for winter activities like skiing, hiking, and mountaineering. Made from 100% Merino wool, it offers excellent breathability, natural moisture-wicking, and odor resistance, which helps keep you comfortable and fresh during physical activity in cold weather. The fabric is knit in an interlock pattern, making it soft and cozy without feeling heavy, and the weight (about 0.26 kg) strikes a good balance between warmth and not being bulky.

The slim fit follows your body's contours, making it easy to layer under other clothing without feeling tight or restrictive. Flatlock seam construction reduces chafing, and raglan sleeves add to comfort and mobility. While Merino wool is naturally durable, it may require gentle care to maintain its quality over time. Some users might find the slim fit a bit snug if they prefer looser clothing.

This base layer is a reliable choice for those seeking warmth, breathability, and odor resistance in a thermal that performs well for outdoor winter sports or everyday cold weather wear, especially when layering is important.

The Cuddl Duds Thermal Underwear for Women is designed for cold-weather comfort, featuring a fleece-lined interior for warmth and a soft exterior for comfort. The material blend of 93% polyester and 7% spandex ensures a snug fit with a bit of stretch, making it comfortable for everyday activities. The set includes both a top and leggings, making it a complete base layer option for winter. The moisture-wicking fabric helps manage sweat, keeping you dry throughout the day.

Additionally, the garment offers 50+ UV protection, adding an extra layer of defense against the sun's rays, and includes thoughtful design features like thumbhole sleeves and a tag-free label for enhanced comfort. The heavyweight nature of the fabric might be too warm for milder winter days, and the snug fit might not suit everyone's preference.

Its sleek design makes it versatile enough to be worn alone or layered under other clothing. Ideal for those who need reliable warmth and comfort in cold weather while enjoying outdoor activities or simply lounging at home.