It's logical to assume that 100% humidity means that the air can't hold any more moisture. This is true, except that other factors can influence how a clothing system dries.
The surface of your garment may not be at ambient air temperature. This may be because it is close to the body and you are generating lots of heat. Some areas, the arm pit, for example, may be better protected from the environment, enabling them to be warmer.
The wind may also have an effect in a number of ways. The downwind areas of your clothing will be in an area of slightly lower pressure, dropping conditions below saturation and enabling evaporation. The wind may flap the fabric, shaking some moisture from the surface and forcing convection inside, and the downwind surfaces may also be better protected from wind chill, encouraging them to be warmer than the upwind areas. Fabrics with a small degree of air permeability (usually undetectable to the wearer) allows warm damp air from the inside to get out. This is replaced by cool damp air which, when warmed, can absorb more moisture.
These aspects of breathability and drying may go some way to explaining why FurTech garments can begin to dry after heavy rain, even though you may still be in the clouds. And this may also explain the feeling of low humidity inside the garments, even after many hours in mist and drizzle.
It's also worth mentioning that once condensation occurs inside a microporous waterproof breathable barrier it needs to be warmed up to a temperature that allows vapour to escape before recovery can occur. If the membrane remains at the dew point, condensation continues to build up. These conventional hardshell waterproof breathable fabrics don't usually allow any airflow through the fabric and aren't as breathable as more air permeable fabrics. The latter point also applies to hydrophilic waterproof breathable barriers.
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