baselayers

It should sit close enough to move moisture away from the skin and layer smoothly, without restricting breathing, shoulder movement or circulation. A loose cotton T-shirt is not an effective technical base layer. Choose a close or athletic fit for active use and a slightly more relaxed thermal fit for low-intensity cold-weather wear.

Merino manages odour well, feels comfortable across temperatures and suits multi-day wear, but it can be slower to dry and less abrasion-resistant. Synthetic fabric dries quickly, is durable and is often better value for high-output exercise. Choose merino for comfort and repeat wear; choose synthetic for intense activity, frequent washing and fast drying.

Wear bottoms when the legs will be exposed to prolonged cold, wind or inactivity, such as winter walking, skiing or outdoor spectating. For active mild-weather walking, a top alone may be enough. Check that tights fit smoothly beneath trousers without bunching behind the knees or making the waistband too tight.

Lightweight fabric suits high-output activity and shoulder seasons, midweight is the most versatile for cool weather, and heavyweight thermals are best for low activity or severe cold. Warmth also depends on the mid-layer and shell, so avoid choosing the heaviest base layer if it will make you sweat during climbs.

Cotton absorbs moisture and dries slowly, so once wet from sweat or rain it can remain cold against the skin. Technical synthetics and wool move or manage moisture more effectively. Cotton may be comfortable for low-risk casual use, but for exposed walking choose a fabric designed to dry and regulate temperature.