wetness

1. The condition of being wet.
2. Moisture.
3. Rainy or persistently damp weather.

Definition: moisture
Antonyms: dryness

Constant wetness of the wool fleece or haircoat along the backs of animals, and caused by heavy rainfall over a long period, causes fleece rot in sheep and rain scald in horses. Constant wetness of the underparts caused by poor drainage in indoor housing, or too little bedding or a defect of urinary control by the animal causes local dermatitis referred to as wet, e.g. wet belly of mink, wet tail of hamsters, wet dewlap of rabbits.

The noun has one meaning:

Meaning #1: the condition of containing or being covered by a liquid (especially water)
  Antonym: dryness (meaning #1)