One of the questions we are often asked is how to regulate temperature, stay warm and dry while walking or climbing, in a variety of weather conditions, without having to buy a complete set of clothing for each season. Although most serious walkers and climbers have a wide range of clothing to suit different conditions it is possible to have a general set to cover most eventualities in spring through autumn.

The theory behind this is called the Layering System, or less well known by the name of "Onionskin layering". It is based on the fact that several thin layers of clothing will keep you warmer than one thick layer. This is because they trap a larger volume of air, and it is this static "reservoir" of air that insulates you from the cold. Not only that but you have a greater degree of control over the level of insulation by adding layers if you are cold or removing layers if you are too warm, far better than having a choice between shivering in a shirt and roasting under a thick sweater! This is very important because sweat is the enemy in cold conditions as it leeches heat from your body and dehydrates you if you produce too much.

More work done in greater comfort with less sweat produced is the holy grail of layering. The layers are known as:

1. Base Layer

Can be a cool shirt with UV protection in hot summer conditions or a thermal insulation layer for winter. It must be comfortable as it is next to your skin all day. This is the hardest working layer as it has to wick all your sweat to the outer layers and is worn the longest.

2(a). Mid layer

Usually a microfleece or similar item. Thin, comfortable light insulating layer. A pullover microfleece with a deep neck zip is my usual choice to allow ventilation if required and can be zipped up to provide greater insulation.

2(b). Outer layer

Thicker, medium weight fleece for optimum warmth with minimum bulk. The mainstay of the cold weather layering system, a full zip version allows more options for insulation/ventilation balancing.

3. Shell

This should be a waterproof, windproof, breathable jacket and trousers (if required). Separates you from the harshest weather conditions allowing a stable environment for the lower layers to perform at their best.

There are a few vital properties that all layers must have for the system to work at its optimum. They must be lightweight, fast drying and, most importantly, have wicking properties. This is the ability of an item of clothing to transport moisture (usually sweat), from the surface of your skin to the outside of the fabric, if all layers do this the sweat will be wicked through them and your breathable shell jacket to be dispersed into the atmosphere. The problem occurs when there is a "weak link" in the chain, that is, a layer which doesn't wick, and acts like a sponge and retains most of the moisture it soaks up making you feel uncomfortable and cold. Cotton is the main culprit for this and it's for this reason that cotton is best used as a fabric to keep you cool in very warm conditions and nowhere else. Otherwise all clothing should be made of synthetic or woollen fabrics. I find fast drying synthetics best.

I have listed my Spring-Autumn and also my Winter layering systems as a guide to what you should be looking to take into the hills with you, but these are only my preferences and you should adjust the list to suit yourself. Some people feel the cold more than others or overheat more easily, you know yourself better than anyone else, so be creative! Remember, the more comfortable you are the more enjoyment you will get from the outdoors. Dress for the worst weather expected, you can always take off layers and pack them away, but if you don't have them with you there is nothing you can do.

Spring-Autumn
Base- Shirt or t-shirt, lightweight trousers or shorts.
Mid Layer- Lightweight /Microfleece or medium weight fleece.
Shell- Lightweight waterproof jacket.

Winter
Base- Thermal base layer (long sleeved, high neck), thermal long johns.
Mid Layer- Microfleece, lightweight trousers.
Outer Layer- Medium Technical Fleece.
Shell- Technical Waterproof Jacket & Trousers.

Extras- Thin liner gloves, waterproof & insulating overgloves or mittens, hat, necksock or scarf.