Thermal underwear is probably among the most important in cold weather. Unless you are out in full summer, drops in temperature are noticeable. When night falls or winds pick up, warmth becomes a necessity. In general, outdoor adventures come with some risks. Always take it upon yourself to be prepared for whatever comes. Just as you would consider emergency kits, consider thermal underwear.
If you ever hike or camp in winter, it is a must. Freezing temperatures and high winds can make it very uncomfortable to move forward. Camp fires are nice, but thermal underwear keeps you warm. Thermal underwear is used as base layers in cold weather. They are worn to fit tightly over your body. And they are meant to absorb moisture keeping you warm and dry.
When choosing thermal underwear, go for spandex or polyester. These are high tech breathable material that wick moisture away. The Icebreaker BodyFit 260 Tech Top is a good example. Try to avoid any cotton thermal underwear unless for indoor use. Cotton retains sweat and becomes heavy when wet. It takes a while to dry which can cause you to get sick.
Under Armor is one recommended brand for thermal underwear. Sierra Designs are also known for their layering jacket sets. The North face Apex Summit is waterproof and wind resistant thermal jacket for winter. Gore-tex has become a major fabric for breathable waterproof outdoor gear. The North Face Meru Gore-Tex jacket is also an example. Tested for Alpine winds, it is a substitution or addition to thermal underwear.
Whether you prefer thermal underwear tops, leggings or jackets, stay warm. There is nothing worse than shaking and gritting your teeth when you are meant to be having some fun. Always consider the temperature changes when outdoors. Think Neck Gaiters, beanies, gloves. Take warm blankets, hand and foot warmers as alternatives to thermal underwear.