10 Best Thermal Underwear Sets 2025 in the United States

The Cuddl Duds Thermal Underwear set for women is designed to keep you warm and comfortable in cold weather. It features a brushed fleece lining inside for extra warmth and a soft, matte finish on the outside. Made of 93% polyester and 7% spandex, it offers good stretchiness, allowing for easy movement and a snug fit that feels comfortable without being tight. The fabric is moisture-wicking, which helps pull sweat away from your skin to keep you dry, making it suitable for active use or layering during outdoor activities. Another nice touch is its protection against UV rays, which is not common in all thermal underwear.

The set includes a long-sleeve top with thumbholes and leggings with a modern rise, designed to stay in place and offer full coverage. Weighing about 15 ounces, it balances warmth without feeling bulky, so you can wear it alone or under clothes. The fabric is durable and machine washable, providing practicality for everyday cold weather use. This set is ideal for women looking for a reliable, warm base layer that combines comfort, stretch, and functionality.

The Merino.tech Merino Wool Base Layer Men's Set offers a high-quality option for those seeking thermal underwear. It's made from 100% superfine 17.5 micron merino wool, which is known for its softness and comfort, reducing the likelihood of itching or discomfort. The set is midweight at 250 g/m², making it suitable for cooler weather without being overly bulky. Additionally, there's an option to select lightweight or heavyweight versions, which gives flexibility depending on the user's needs.

This set also includes a pair of merino wool hiking socks, adding extra value to the package. The moisture-wicking and odor-resistant properties of merino wool are significant benefits, ensuring that users stay dry and fresh even during prolonged wear. This makes the set ideal for outdoor activities or long days of wear. The breathability of the material helps to regulate body temperature, enhancing comfort throughout different seasons.

Durability might be a concern as the product requires hand washing and air drying to maintain its longevity. This could be inconvenient for some users who prefer machine-washable options. Additionally, although the set is designed to avoid issues like rubbing or bunching, the fit might still vary depending on individual body types. Users who prioritize high-quality, comfortable, and functional thermal underwear will find this set beneficial, especially for moderate to intense outdoor activities.