Let's start with the basics of how to layer for cold weather. The 3-layer rule recommends you build your winter outfit around three key layers: base, mid-layer, and outer shell.
The base layer offers warmth and comfort, but its primary purpose is moisture wicking, drawing sweat away from your skin to keep you dry. The mid-layer is for warmth — it should trap heat. The outer layer is your protective shell, keeping out harsh winter elements like rain, wind, or snow.
Finally, don't forget accessories like winter boots and gloves to keep extremities covered.
Across all three layers, you want to achieve a combination of warmth, breathability, and mobility. It's important to choose the right materials for each layer.
For example, cotton is a poor choice as a base layer because it absorbs moisture, dries slowly, and doesn't insulate well when wet, leaving you cold and damp. Synthetics and merino wool do a much better job of wicking moisture away to keep you dry.
For your mid-layer, look for good insulators, like fleece, down, or wool. For the outer shell, materials that are waterproof, windproof, and breathable (like Gore-Tex) are best.
And don't forget to keep cool. If you wrap up too warmly, you'll quickly get sweaty and clammy as your body heats up through movement. If you expect to be active, dress to be a little cooler than you'd like — because you're going to warm up as you start moving.