Outdoor enthusiasts have long recognized that multiple layers of clothing keep them warm in winter and from overheating in summer. Adding or removing garments is a practical way to adapt quickly to different activity levels and temperature changes during your time outside.

Many winter campers wear a system of underwear, a midlayer of polyester fleece (pants and top), followed by a windproof, water-resistant outer layer (windpants with full zips down the side for easy on/off and a high-performance wind shell with zippers under the arms for ventilation during active sports).

While cotton was once the mainstay of long underwear and cold-weather clothing, it is no longer recommended for strenuous winter activities because it soaks up moisture. Damp clothes are heavier and, if next to your skin, can pose a chilling hazard.

Modern performance underwear, made from polyester or polypropylene, is most effective in moving moisture away from your skin and into outer layers of clothing where it can evaporate.

In addition to traditional shirts and "long johns," many other garments, including short-sleeve tops, bras, boxer shorts and briefs, are now made with polyester fabrics to wick away chilling perspiration.

If you are performing an active sport such as skiing, or hiking in spring or fall, a polyester fabric, such as fleece, is an ideal second layer over your long underwear. It continues to trap your body warmth while wicking away moisture. Even in warmer seasons, a midlayer is useful to have handy in your pack for those times you begin to chill (particularly during rest stops.)

Depending on weather conditions, you may want to wear wind-resistant, water-resistant pants and an anorak over your other clothes. How many layers you need depends on your level of exertion, personal preference and weather conditions.

Be prepared for severe weather. Carry a waterproof rain jacket and pants with you, even if the forecast is for sunshine.

Up to 80% of your body heat can be lost through your neck and head. Carry a hat with you for added warmth or protection from the sun.

For overnight trips, carry a lightweight polypropylene hat. It stores compactly in your pack pocket and doubles nicely as a comfortable sleeping hat in cool weather.

Winter campers often carry a hat system consisting of a lightweight polypropylene liner and a nylon shell to adjust to changing winter temperatures.

For maximum comfort and blister prevention, many hikers wear two layers of socks, a thin polyester sock liner with a thicker outer sock. On overnight or extended trips, be sure to carry enough socks to be able to change into a fresh set each day.

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