Outdoor Base Layers & Thermals

Outdoor Base Layers and Thermals for Better Layering

Base layers are the foundation of an effective outdoor clothing system. Worn next to the skin, they can help manage moisture, add warmth and make it easier to stay comfortable as your activity level and the weather change.

Explore base layer tops, bottoms, matching sets and thermal underwear for men, women and children, with options suited to everything from everyday winter walks and camping trips to hiking, skiing, cycling and more demanding outdoor activities.

What Does a Base Layer Do?

A base layer sits beneath your other clothing and is designed to help create a comfortable environment next to the skin. During active use, moisture management can be particularly important because damp clothing may quickly become uncomfortable when you slow down or temperatures fall.

In colder conditions, base layers also form the first part of a layering system. A base layer can be combined with a fleece or other midlayer for insulation, followed by a suitable outer jacket when protection from wind, rain or snow is needed.

Base Layer Tops, Bottoms and Sets

Base layer tops are available in different weights and styles, from lighter garments intended for active use to warmer thermal tops for colder conditions. Long sleeves provide greater coverage, while the fit and fabric can influence how comfortable a layer feels underneath other clothing.

Base layer bottoms or thermal leggings provide similar protection for the legs and can be worn beneath walking trousers, ski clothing, workwear and other outdoor garments. Matching base layer sets offer both top and bottom layers together and can be a convenient option when you need full-body coverage.

Merino Wool or Synthetic Base Layers?

Merino wool and synthetic fibres are two common choices, and each has different advantages. Merino base layers are valued for warmth, softness and their ability to remain comfortable across a range of temperatures. They can be particularly useful for longer days outdoors or activities where you may not be able to change clothing regularly.

Synthetic base layers often dry quickly and can work particularly well for higher-intensity activities where you expect to generate more heat and perspiration. They can also be a practical choice for running, cycling, hiking and other activities involving sustained movement.

Neither material is automatically the better choice. Think about how active you will be, how cold the conditions are likely to be, how quickly you need the garment to dry and how long you expect to wear it.

Choosing the Right Thermal Base Layer

Warmth is important, but choosing the thickest thermal layer is not always the answer. During strenuous activity, too much insulation can lead to overheating and leave you feeling damp once you stop moving.

Lighter base layers can suit milder conditions and energetic activities, while heavier thermal layers may be more appropriate for colder weather, slower-paced activities or situations where you will spend periods standing still.

Fit also matters. Base layers usually work best when they sit relatively close to the body without feeling restrictive. A loose garment may be less effective at managing moisture, while one that is too tight can limit movement and become uncomfortable beneath additional layers.

Base Layers for Different Outdoor Activities

Walking and hiking base layers need to remain comfortable over extended periods and work effectively beneath changing layers. Skiing and winter sports can demand greater warmth, while cycling and running often place more emphasis on breathability and moisture management.

For camping, fishing, shooting, outdoor work and other activities involving periods of lower movement, retaining warmth may become a greater priority. The most suitable choice therefore depends as much on what you will be doing as the temperature shown on the forecast.

Caring for Base Layers and Thermals

Technical fabrics and merino wool can have specific washing and drying requirements. Using the correct washing method can help maintain the fabric’s feel and performance, so always check the individual garment’s care instructions before cleaning.

Browse outdoor base layers and thermals by user, garment type and material, then consider the expected temperature, activity level and other layers you plan to wear when choosing the most suitable option.