Many people have put on a waterproof jacket, gone for a brisk walk and arrived with a damp shirt, even though not a drop of rain has come through. The moisture has come from the inside. When you are active, your body gives off warmth and moisture, and if the jacket cannot let that escape, it condenses on the inner lining. Understanding this makes it easier to choose and wear your clothes sensibly.
The first step is to control how warm you get. If you wear too many layers under a waterproof jacket, you will sweat sooner, and the moisture has nowhere to go. Start a walk feeling slightly cool, because you will warm up soon after you begin moving. Take a layer off before you become hot, rather than after you have already begun to sweat.
Vents, layers and fabrics
Use the vents that many jackets have: zips under the arms, a front zip that can be opened a little, or cuffs that can be loosened. Opening these for a few minutes lets warm, damp air out. If the rain is light, you can leave the hood down as well and let your head cool. Close everything again when the shower gets heavier and the wind picks up.
What you wear under the jacket also matters. A thin base layer made of wool or a quick-drying synthetic fabric moves moisture away from the skin. Cotton absorbs it and holds it against you. Choose looser clothes in the middle, rather than tight ones, so that air can circulate and carry the moisture out. A rucksack pressed against your back can also trap heat, so give it a rest now and then.
Look after the jacket, too. Dirt, sweat and body oils can clog the fabric so that it breathes less well. Wash it according to the label, with a gentle detergent, and rinse thoroughly. Then let it dry fully before use. A clean jacket lets moisture escape more easily and keeps the outer surface working properly. Combine all these habits and you should stay much drier, even on a long, brisk walk.
