In reply to druridge:
I think I've decided that 'dry' isn't always possible and 'warm and moist' is fine. I reckon Andy Kirkpatrick nudged me in that direction, and volunteering in a bright orange and unbreathable waterproof did while wearing wool things underneath it, I'd quite a nice warm fug generated inside by the end of the day from walking about doing stuff, being warm is the main thing when we've a waterproof skin. Unless one's sweat might freeze I suppose, which I've never been in a cold enough environment for.
Post edited at 16:57