Properly layering your clothing is essential to staying warm and comfortable in the cold. A simple mnemonic device can help you remember the basics of dressing for winter activities outdoors.
W is for Wicking.
First you’ll want a (non-cotton!) next-to-skin base layer that is both warm and effective at moving body-chilling moisture (a.k.a. your sweat) away from your skin and out of your clothing system. This layer should be as form-fitting as possible without being constricting in any way.
I is for Insulation.
Next comes your insulating layer, typically a fleece or down jacket, which provides the majority of the warmth. As a general rule, the thicker the insulating layer, the warmer it will be. Keep in mind that you may not need this layer during periods of heavy exertion.
S is for Sheltering.
This is your outer layer, which protects you from wind and precipitation. Depending on conditions, it might be an ultralight windbreaker, a breathable and water-resistant soft shell, or a fully waterproof but less breathable hard shell featuring Gore-Tex or an equivalent.
E is for Extra.
It’s smart to carry an extra layer in the event of changing weather, an emergency, or an unexpected night out. This can range from a down vest for your core to a puffy go-over-everything down or synthetic-fill jacket.