Cold air holds almost no water, and heated air holds even less of what it could
Absolute against relative humidity, why a heated room in January is harder on skin than the beach it came from, what wind does mechanically as well as evaporatively, and where cold responses stop being ordinary.
Cold air is dry air: the physics behind winter skin
Cold air holds very little water even when it is saturated. That single fact explains most of what happens to outdoor skin between November and March.
Cold · Humidity · 10 minWhy winter indoors is often worse than winter outdoors
You spend far more hours in heated air than in cold air, and heated air in winter has a lower relative humidity than the outdoors it came from. The maths favours the beach.
Cold · Indoors · 10 minWind: evaporative and mechanical stress in one exposure
Wind does two separate things to skin, and only one of them is about drying. The other is abrasion, and it is why the same wind on a sandy beach is worse than on a hillside.
Cold · Wind · 10 minHand skin in cold water, and why it recovers so slowly
Hands take the worst of a cold water session and are also the site that recovers most slowly. The reasons are structural, circulatory and mechanical at once.
Cold · Hands · 10 minCold related skin responses, described and referred
Skin does several recognised things in response to cold, from ordinary flushing to reactions that need proper assessment. Where the line is, and why we do not cross it.
Cold · Referral · 10 minWindburn: three mechanisms with one appearance
A red, hot, tight face after a long exposure gets called windburn. At least three different processes produce that appearance, and they need different responses.
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