Relative humidity does not measure mugginess.
As I indicated at the end of the recent post about surface tension, I've started a new thread about the amazing properties of water. This time I'll write about saturation, what it is and what it isn't. The reason I included the bit about "what it isn't" is that a close friend once asked what saturation actually was - they thought that if the air were "saturated" it was like walking through a swimming pool. Not an unreasonable deduction based on our everyday meaning of "saturation".