Thermal Underwear
Thermal underwear, also known as long underwear or base layers, is essential for staying warm in extreme cold weather. These moisture-wicking garments form the foundation of effective layering, keeping you dry and warm whether you're active or stationary in cold conditions.
Best Thermal Underwear
Top-rated long underwear and thermal base layers
Smartwool Merino 250 Base Layer Top
Patagonia Capilene Midweight Top
Arc'teryx Rho LT Base Layer
Smartwool Merino 250 Base Layer Bottom
Patagonia Capilene Midweight Bottom
Icebreaker Merino 200 Oasis Top
Frequently Asked Questions
Thermal underwear, also called long underwear or base layers, are insulating garments worn next to the skin. They provide warmth, wick moisture, and are the foundation of effective cold-weather layering systems.
For extreme cold (below 20°F / -7°C) or extended outdoor exposure, thermal underwear significantly enhances warmth and comfort. For milder conditions, a regular shirt or sweater may suffice, but thermal underwear provides better moisture management.
