Humidity
Humidity was the amount of water vapor in the air; where relative humidity was the ratio of the actual amount of humidity present in the air to the maximum humidity possible at the same temperature, expressed as a percentage.

On the planetary file for Draygo IV, it was noted that the planet had a "humidity factor". ()

The ideal moisture level to grow mycelium spores in the cultivation bay was approximately 85% to 87% relative humidity. ()

After Deanna Troi became infected with Barclay's Protomorphosis Syndrome and began transforming into an amphibian, she requested that the ship's computer "increase ambient temperature by two s Centigrade and increase relative humidity by ten percent." ()

External link 
 
Meteorology
Measurements