10 Best Thermal Underwears 2025 in the United States

The Cuddl Duds Thermal Underwear for Women is designed to keep you warm and comfortable during cold weather. Its main strength lies in its material composition of 93% polyester and 7% spandex, which makes it both flexible and snug, accommodating movements without feeling restrictive. The brushed fleece lining adds an extra layer of warmth, making it an excellent choice for very cold climates or winter outdoor activities.

Weighing around 14.89 ounces, this thermal set is relatively lightweight, which enhances comfort without sacrificing warmth. The moisture-wicking fabric is a valuable feature, as it helps absorb and quickly evaporate moisture, ensuring you remain dry and comfortable, particularly when engaging in physical activities.

Fit-wise, the thermal set includes a modern rise leggings and a top with thumbhole sleeves, offering a stylish twist while preventing drafts and retaining heat. The inclusion of spandex provides a comfortable stretch, allowing the garment to move with you, which is ideal for active wear or layering under other clothes. However, some users might find the fit too tight if they prefer a looser base layer, so considering sizing up might be beneficial.

In terms of UV protection, the set offers a 50+ protection rating, providing peace of mind for those who might be exposed to sunlight during winter sports or activities. This feature, along with the tag-free label, enhances comfort and wearability. Potential buyers should note that the product is imported, and care instructions suggest machine washing, which is convenient for maintenance. The Cuddl Duds set is an ideal option for women looking for a versatile and effective thermal base layer, suitable for both outdoor and indoor use during the colder months.

The Cuddl Duds AMAZON WMS TP - L/S Black thermal underwear set is designed for cold weather, featuring a brushed fleece inside and a soft matte outside for added comfort. Made from a blend of 93% polyester and 7% spandex, it offers good stretch and flexibility, ensuring a snug fit that can move with you.

The spandex stretch and modern rise leggings provide on-the-go comfort, while the thumbhole sleeve top and tag-free label enhance wearability throughout the day. The set also includes moisture-wicking fabric, which helps absorb and evaporate moisture, keeping you dry and comfortable. Additionally, it offers 50+ UV protection, adding an extra layer of defense against harmful rays.

Weighing in at 14.89 ounces, it is lightweight enough to wear as a base layer or on its own. However, the heavyweight fabric might feel too warm in milder temperatures, and while it is machine washable, the 93% polyester composition may not be as breathable as natural fibers. Ideal for those who need reliable and warm thermal underwear for outdoor activities or everyday use in colder climates.

The Merino.tech Merino Wool Base Layer set is a versatile choice for men looking for comfortable thermal underwear. Made from 100% superfine 17.5-micron merino wool, it promises softness and comfort without the itchiness you might get from other materials. This set includes a midweight top and bottom with a weight of 250 g/m², making it suitable for a variety of conditions. Additionally, it comes with a free pair of Merino Wool Hiking Socks, which adds extra value to the package.

One of the standout features is its moisture-wicking and odor-resistant properties, which help to keep you dry and fresh throughout the day. The wool's natural breathability also aids in regulating body temperature, making it a good option for year-round wear. On the downside, the set requires careful handling for longevity. While it can be machine washed, hand washing and air drying are recommended for best results, which might be less convenient for some users.

The price point may be higher compared to synthetic alternatives, but the added comfort and performance of merino wool could justify the cost. This base layer set is a solid pick for those who prioritize comfort, moisture management, and temperature regulation in their thermal wear.