[sammyg2]

I found this which is of interest and seems reasonable:

Q: Is it possible for relative humidity to be higher than 100%?

A: Yes, it is possible. In Elements of Meteorology the authors Albert Miller and Jack C. Thompson explain that in extremely clean air which contains no "foreign" particles, water droplets, or ice crystals it is extremely difficult for condensation to occur even when supersaturated conditions are present. Supersaturated conditions refer to relative humidities much greater than 100%. C.T.R. Wilson invented an instrument called a cloud chamber in which clouds can be manually made. He discovered that in pure, clean air the relative humidity must reach 800% before water drops form. Realistically, air is not pure and clean. There are many particles that are small enough to remain suspended in the atmosphere such as salt particles from sea water, combustion products, meteoritic dust, volcanic material, and soil. These particles, prominent as they are, act as nuclei for water to condense upon and, hence, are an easier means of condensation. This means that condensation in real air can usually produce humidities just barely over 100%.

USATODAY.com