The clothes you take outdoors are called a layering system because the pieces work together to keep you warm, dry, and comfortable. It’s not complicated: Swap, add, or drop layers as conditions and your level of exertion change. But the better you are at adjusting layers to stay in the sweet spot and avoid getting too hot or too cold, the longer you’ll be able to stay out and the more you’ll enjoy it. Here are the key pieces of any layering system and how to manage them.

Baselayer

Your next-to-skin layer comes first: In milder weather, that’ll be a short-sleeve or long-sleeve top on its own. In cold weather, you might need baselayer bottoms (long johns) under your pants as well. A baselayer’s job is to wick sweat away from your skin so you stay dry—getting wet quickly leads to getting chilled, which can be downright dangerous in cold weather. Most baselayers are made of merino wool or synthetic fabrics like polyester or nylon. Avoid cotton, which absorbs moisture and dries slowly (though it can be a good choice in the hottest weather).  Baselayers should fit fairly snugly for the best moisture management, but not so tight as to constrict movement.

Midlayer

Next come midlayers, which are slightly thicker and warmer than baselayers and range from vests to full-zip light jackets. Wear one when it’s too cold for just a baselayer top, or pull one on during rest breaks (your body will quickly cool down when you stop moving). You might also want to sleep in one for extra insulation. Midlayers come in a variety of fabrics, from gridded fleece to merino wool. They should fit fairly snugly as well to help them layer under warmer jackets smoothly.

Insulation

This is a puffer jacket made with down or synthetic fill, and it’s really just a warmer midlayer. A puffer is a must for fall, winter, and spring—plus summer, if you’re spending time at higher altitudes. Insulated jackets are great for pulling over midlayers during rest breaks and when you reach camp; they’re typically too warm to wear during any strenuous activity, unless it’s really cold. They range from ultralight jackets perfect for summer alpine backpacking trips to bulky parkas meant for mountaineering expeditions.

Outer Layer

Your final layer is your strongest protection against the weather. You have three options: a hardshell, softshell, or windshell.

Hardshells are fully waterproof, windproof jackets that protect you (and the rest of your layers) from wet, breezy conditions. You’ll want to pack one if there’s any chance of rain or wet snow. Hardshells feature waterproof/breathable technology that allows body heat to escape while still keeping precipitation out, but even the best still sacrifice some breathability. You might want to take off your midlayer when you put on a shell to help prevent overheating; also take advantage of any vents (like pit zips) on the shell as you hike. In persistently wet conditions or climates, hardshell pants that fit over your regular pants are also a great idea.

Softshells, on the other hand, aren’t fully waterproof, though they usually have some kind of water-repellent treatment on the exterior. They provide some level of wind protection (but might not be fully windproof), and they’re usually stretchy. Because of that, softshells are more breathable and comfortable to hike in. They’re ideal for dry, cool weather, when you’re sure you won’t need full waterproofness. Tip: Some softshells work well as midlayers, layering nicely under a hardshell when you need it.

A windshell (which could be considered a type of softshell) is a lightweight layer meant to repel wind. Most are treated with DWR for some protection against light precipitation, too. They’re great for breezy alpine conditions in milder weather or highly aerobic activity in cooler weather, but don’t provide much warmth.

Size all your outer layers to fit comfortably over your typical baselayers and midlayers. 

Mix and Match

It takes trial and error to learn which layers to pack for every trip. You need to know your own body (do you run hot or cold?), pay attention to the forecast, and decide how to balance weight and bulk versus having extra “insurance” layers. Here are a few sample scenarios:

Summer, lows in the 50s, with rain: Baselayer, midlayer, hardshell.

Fall, lows in the 30s, dry and windy:  Baselayer, midlayer, puffer jacket, softshell. 

Winter, lows in the teens, snow: Baselayer, midlayer, heavyweight puffer jacket, hardshell.

Tips For Managing Layers

Now that you know the pieces, here’s how to use them.

• Start out a little chilled. You’ll warm up quickly when you start moving, so bundling up at the trailhead probably means you’ll need to stop in five minutes to take something off.
• Adjust layers frequently. If you start to overheat, shed a midlayer or shell; if you’re cold, add insulation. It’s much easier to maintain the proper body temperature than to warm up or cool down once you’ve veered off course.
• Keep in mind that switching layers can only do so much. Also adjust your pace to stay in the comfort zone—speed up if you’re getting cold, or slow down if you’re sweating buckets (in cold weather you want to avoid sweating, which will get your baselayer wet and chill you when you stop).
• Pull on a hardshell as soon as it starts raining—a wet baselayer won’t be able to do its job of wicking sweat and keeping you comfortable. In moderate temps, wearing a hardshell might mean you need to slow down to avoid overheating and getting wet from the inside.  
• Put on a warmer layer (midlayer and/or insulation) as soon as you stop for a break or arrive in camp. Take it off when you start moving again.

All articles are for general informational purposes.  Each individual’s needs, preferences, goals and abilities may vary.  Be sure to obtain all appropriate training, expert supervision and/or medical advice before engaging in strenuous or potentially hazardous activity.