Outer Layer (waterproof layer)
The cooling effect of cold water on warm skin is a good thing if the body is in a state of overheating. However, when insulation from heat loss is required, cold water next to the skin can have fatal consequences. The aim of wearing an outer layer is to keep water out and simultaneously release the moisture created by the body. Your outer layer needs to be not only waterproof but also breathable.
There is a wide range of waterproof jackets and trousers available from walking shops in a number of different styles and fabrics. Two popular ones are Gore-Tex and eVent.
The jacket needs to be large enough to go over your fleece and other insulating layers. It should have an attached hood and a full length front zip (this will aid ventilation) with storm closure.
Waterproof trousers are important in keeping you warm and dry. All the water runs off your jacket onto your lower body. Trousers should have have leg zips long enough so that you can pull the trousers on and off over your boots. If you leave your waterproof trousers on when there is no need, your legs will overheat and quickly become tired.
Your waterproof/breathable garments in particular need to be looked after if they are to stay waterproof and breathable. At the end of your expedition make sure they are clean and dry before being stored away. Follow the manufacturer’s care label when washing and re-proofing.
Gloves need to be waterproof and insulated for warmth, with long enough cuffs to go up into the sleeve of your waterproof jacket. It is very difficult to keep gloves dry, especially if you are constantly taking them off and on. It is important, therefore, that they should remain functional when wet. Wool, fleece or fibre-pile gloves with waterproof over-mitts is a good combination.
You lose a lot of heat from your head, so it is essential to wear some form of protection if you are to remain warm. Both fleece and wool are suitable but need to be large enough to cover your ears.
In strong sun a light wide brimmed hat provides protection, not only to your head, but also to your face and neck. A chin strap or some other method to stop it being blown away is useful. If you wear glasses, a peak can help keep the rain off. A baseball cap worn under the hood of a cagoule in bad weather keeps your head warm and the rain off your face.