This is an irregular verb. It follows the conjugation pattern of the verb vencer.
This verb is mainly used in Brazilian Portuguese. In European Portuguese, humedecer is preferred.
Present:
A Ana umedece o pano antes de limpar.
Ana moistens the cloth before cleaning.
Preterite:
O Miguel umedeceu a terra antes de plantar.
Miguel dampened the soil before planting.
Conditional:
A Clara umedeceria a superfície levemente.
Clara would moisten the surface slightly.