Best Base Layers For Changeable Autumn Weather

Autumnal weather is often unpredictable. You can go from scorching hot days to mornings with ground frost, so your clothing needs to be flexible. One essential item you should be carrying in your backpack is a good quality base layer. 


Wearing clothing that will adapt to both hot and cold conditions is ideal for Autumn weather. A base layer top may be all you need to put on as it will insulate your core in cooler weather, but not so much as to cook you when the sun comes out.

The tricky part is finding out how warm a base layer is. A simple, but underused test, is the TOG. This international standard measurement gives the thermal resistance rating of a fabric.  You have probably seen it used on duvets, mattresses and pillows, and the lower the figure, the less insulating it is.

In the Autumn you need a lightweight thermal underwear brand that has a TOG rating of between 0.35-0.55. Anything higher and you are going to be too warm, anything lower and your body could start to chill.

Our Factor 1 Plus base layers have a TOG rating of 0.47 making them a great choice for thermal underwear. 


If you are working hard in any weather conditions, you are going to perspire. A good quality base layer should be able to actively manage this process by being able to 'Wick'. What this means is basically how quick perspiration is moved from the skins surface to the outside surface of the fabric, so it can evaporate or be moved on to the next clothing layer.

The best lightweight thermal underwear garments will have a hydrophilic treatment applied to them. These chemicals actively aid the movement of moisture – hydrophilic means water loving – so vastly improve the fabrics own moisture transportation system. In the cooler Autumnal weather this process keeps a dry layer of air next to the skin (air being the insulator) helping you to keep warm. In warmer weather you will probably wear the lightweight thermal underwear on its own. A quick wicking rate will pump moisture out to the surface of the thermal and allow evaporation. This will help to cool you as water has a high heat capacity and needs a lot of energy to phase change i.e. transform from a  liquid to a gas.  In layman’s term, your excess body heat is absorbed by the water on the fabrics surface to change to a gas,  or evaporate as us mere mortals know the process.


Base layers should be snug fitting. By snug we do not mean restricting blood to an appendage so it goes purple with loss of circulation.  The base layer must be close fitting so no air can be wafted when you move. For someone who has not got the body of David Beckham this is not going to be a pretty sight as a good fitting thermal will contour to all your lumps and bumps. However, this close fit ensures that air is trapped next to the skin, insulating the wearer. It also aids hydrophilic treatments as they only work efficiently when there is a heat gradient. The best way to achieve this is by having the fabric in close contact to the skin.

The best lightweight thermal underwear garments will also be constructed sympathetically to your activity. Look for thermal underwear that has a long body length so when you bend over to pick something up or tie your shoe laces your lower back does not become exposed. The sleeves should also be of a significant length that when you lift your arms they do not ride up and expose much your skin.

Our Factor 1 Plus base layer range also has the advantage of  thumb holes near the cuffs, helping to prevent the sleeves riding up when putting on another layer or outdoor jacket.


It might not sound as if it would make much difference, but your choice of base layer colour will actually affect how hot or cold you feel. The colour black for instance, is a good absorber of light wavelengths and will attract more energy from the sun than a lighter colour. However, black is also a good radiator of heat so in overcast weather it will loose heat quicker than a lighter colour. White on the other hand, reflects heat the best as it absorbs very little light.


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