The humidity by itself is not a problem. The real problem lies in condensation. If there is condensation on the sensor, lens, internal mechanisms, the end result will be some sort of permanent damage requiring factory repairs.
It is for this reason that pro photographers in colder climates like the Arctics leave the outdoor cameras stored OUTDOORS.
As Ubrales said, its not the humidity but more the condensation. And it all depends on the amount of humidity/condensation. Being in high humidity might cause condensation around lens and affect pictures.