Introduction

Layering various combinations of clothing pieces helps hikers manage thermal comfort and moisture in response to changes in activity level and environmental conditions.

Generally, layers for backpacking should be hydrophobic (so as not to absorb excessive moisture, whether from perspiration or precipitation), quick to dry, and lightweight.

Clothing that absorbs as little moisture as possible (i.e., is hydrophobic and lightweight) dries faster and remains lighter if you have to stow it back in your pack. In addition, the less moisture that is absorbed in your clothing, the less likely you will be chilled by evaporative cooling. Evaporation of moisture in clothing requires body heat. Excessive loss of body heat can be uncomfortable or unsafe in cold conditions.

Traditional layering systems for inclement weather are based on their ability to serve three primary functions:

  1. Wick perspiration away from the skin surface.
  2. Keep you warm via insulation and wind-blocking.
  3. Keep you dry and protected from precipitation.

These three functions are addressed by what is commonly referred to as the three-layer system.

three pieces of clothing labeled "wicking" (polyester base layer), "warmth" (polyester fleece mid layer), and "wind/rain" (waterproof nylon).
A traditional three-layer clothing system for backpacking. The wicking (“base”) layer is most commonly a polyester knit shirt. The insulating layer may be a high-loft polyester fleece or pile. The outer (“shell”) layer is a waterproof (and often, breathable) layer that is impermeable to wind and outside precipitation.

The layering system illustrated above includes three garments popular in the backpacking community and weighs a total of 31.3 oz (887 g):

In the three-layer model, the wicking layer is worn in warm conditions, the warmth layer is added in cold and dry conditions, and the wind/rain jacket is layered over either the wicking layer alone (e.g., in cool and drizzly or dry, cold, and windy conditions) or over both the wicking and warmth layer (e.g., in very cold, wet, and windy conditions).

Author’s Note: An ultralight backpacker will look at the specific three-layer system example above and be appalled at the weight! For example, my mid-summer alpine hiking system in the US Rocky Mountains includes a 115 gsm (gram per square meter) merino base layer (4.5 ounces / 128 g), a 60 gsm Polartec Alpha Direct hoody (3.5 ounces / 99 g), and a 7D waterproof trail running smock (3.1 ounces / 88 g), for a total system weight of 11.1 ounces (315 g): a system that’s about a third of the weight of the one illustrated in the image above.

About the Weight of Your Clothing Layers

The purpose of layering is not to save weight; it’s to increase comfort and versatility in response to changing activity levels and environmental conditions. However, selecting the lightest possible layers to accomplish this objective makes obvious sense. Lighter layers (less material) absorb less water and dry faster. Lighter layers provide less material resistance in response to body movement and feel more comfortable. And, of course, when stowed in your pack while not in use, lighter layers are, well, lighter.

Layering for Shoulder Seasons

Shoulder season refers to spring and fall when the weather is predominantly characterized by wet, cold, and windy conditions (as opposed to the dryer and warmer conditions of summer and the dryer and colder – subfreezing – conditions of winter). I find it easier to stay comfortable during the snowy subfreezing cold of winter than during the wet, cold, and windy conditions that occur between Labor Day and Thanksgiving or between Easter and Juneteenth (at least where I do most of my hiking in the Colorado, Wyoming, and Montana Rockies). In addition, backpacking during shoulder seasons brings fewer daylight hours and more time spent in camp, where it’s harder to stay warm while inactive.

The three-layer system presented above starts to break down in shoulder season conditions, especially when precipitation starts to fall.

group of hikers in a sleet storm hiking through the forest
Bushwhacking towards the treeline, en route to a high alpine pass crossing – into a September sleet storm. Temperature 34 °F (1 °C). Location: Absaroka-Beartooth Wilderness, Montana. On this trip, where we (as guides and instructors) espoused the ethos of ultralight, many of us were envious of the lone participant wearing the well-ventilated and more durable Arc’teryx Beta LT Jacket.

Using Ventilation to Resolve Overheating While Hiking in the Rain

During the summer in the mountains of the Northern Rockies (MT, WY, and Northern CO), in the Pacific Northwest (WA and OR), and the Inland Northwest (e.g., Idaho Sawtooths, Uintas), shoulder season conditions can occur any time of year on a regular basis. If you are hiking in any of these areas on extended trips where you can’t accurately forecast the weather, plan on preparing for shoulder season conditions.

Barring any unusual weather patterns, most of the other mountains of CA, UT, NV, AZ, and the entire Appalachian corridor are characterized by warmer temperatures where a typical three-layer system will suit most hikers just fine.

The risk of discomfort and even hypothermia goes up significantly when the combination of cold temperatures (in the 50s °F / 10s °C or lower), heavy or sustained precipitation, and even just light winds (greater than about 10 mph / 16 kph) are coming at you during the day when you are facing several hours of hiking. I bring this up because the combination of cold, wet, windy conditions is something every hiker should be sensitive to, regardless of their geographic location or date.

When hiking in the cold-wet-wind trifecta, one of the biggest issues hikers face is that of overheating while wearing a waterproof shell. Let’s address that issue now.

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