To dress properly for cold-weather outdoor adventures, you need to keep two key principles in mind.
Dressing in layers lets you regulate your temperature by adding or removing items as the day goes on. Each layer also traps insulating air, and has a specific job to do. Base layers suck moisture away from your skin, bulkier mid-layers provide insulation, and the outer layer keeps out wind, rain and snow.
Always avoid apparel made of cotton, which is cold, heavy and slow to dry. Merino wool or light synthetics, which wick moisture and dry quickly, are ideal fabrics for base layers. Good mid-layer materials include fleece, heavier wool and down. Outer layers should be made with waterproof, breathable material, such as Gore-Tex or OutDry.