Why does cold weather dry my skin out? Generally things dry out more slowly the colder it is, yet as soon as winter arrives my hands become so dry the skin splits.
• Air at a given temperature can hold only a certain amount of water vapour: the colder it is, the less it can hold. In cold weather, this saturation level is so low there is very little water vapour in the air, even if the relative humidity (the ratio of the amount in the air to the saturation value) is high.
The rate of evaporation from a moist surface depends on the difference between the concentration of vapour in the air right at the surface and the concentration in the bulk of the air. The former depends on the temperature of the moist surface: in the case of your skin, it is warm even in cold weather, whereas ...
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