Year-round, it’s important to have layers in the Pacific Northwest for any outdoor activity, but none moreso than hiking. Weather can change drastically from morning to high noon to night, and being prepared for the elements is vital. But when do you need a midweight layer or a thermal layer? What is long underwear? And why can’t I just bring a sweatshirt?
Typically, there are three types of layers–the base layer, or the one closest to the skin (except a bra). It can be a tank top, t-shirt, or long-sleeve shirt, and can include tights or long underwear bottoms. Material is the most important factor in a base layer. Cotton is rotten (and in some situations, cotton kills). Cotton soaks up water like a sponge and holds it against your skin, dramatically lowering your body temperature and at best, giving you a miserable experience (at worst, hypothermia). Your best options for materials are either merino wool or a synthetic moisture-wicking material for a base layer. They both have their pros-and-cons——wool products are very expensive and not always animal-friendly, but synthetic ones can leach microplastics into the environment and can get very smelly after a few uses.
Many companies make their layers in different ‘weights’ or thicknesses–for instance, Patagonia makes a ‘lightweight’ base layers for warmer days, ‘midweight’ base layers for cooler days, and ‘thermal weight’ base layers for snowy or cold conditions. Personally, I like using lightweight or midweight even on cold days for tops, but have a pair of thermal weight tights–it’s easier to add layers on to the top than bottoms for me. On hot days, sometimes wearing a long-sleeve shirt can be nicer than a tank top or t-shirt for the added sun protection!
Next, if needed, is your mid layer or insulating layer. This is what you wear for warmth over your base. Good choices here are fleece or insulated (down or synthetic) jackets or vests. I love North Face Denali fleece jackets and my Patagonia Nano Puff vest–the vest packs down into it’s own pocket, making it easy to bring along just in case I’m unsure of conditions. Typically your midweight can also be classified into ‘light’ ‘medium’ or ‘thermal’ weights as well. For cold winter activities, a big tenant is ‘be bold, start cold.’ Once you start working hard in the snow, you can work up a sweat, fast. Sweating in snowy conditions can cool down your body too quickly, so it’s better to start at a colder temperature and add layers if needed than to start as bundled as Ralphie from A Christmas Story and be drenched in sweat a half-mile in. For this reason, unless you’re in subzero temperatures, I would not recommend a thermal base and a thermal mid layer at the same time–and I run seriously cold.
Your final layer is the outer layer, sometimes called the shell layer. This last layer is your protection from precipitation and wind or the sun. You can go light, like my beloved Brooks windbreaker or an ExOfficio BugsAway hoodie, or go seriously heavy for those torrential downpours. The lighter a outer layer, the better it will breathe, but the less protection. Rainproof pants or snow pants are great examples of outer layers to be worn over your base.
With winter coming, I’ll be scanning sales to load up on a few more layering options. You can never have too many fleece jackets or flannel shirts! It’s easy to build your hiking wardrobe slowly to have enough options for a multitude of options–which sure came in handy that crazy weekend in Winthrop where it was 60* and sunny one day, and snowing the next!