There can be quite a bit of condensation if I let it sit for a long time without drying it up. I do have a vent in the bathroom that gets used when the shower is on. No windows. I don't think the range in temperature throughout the day is that great, but the water temperature may be something to check out. I'll check tonight.
Come to think of it, this started around the time when we changed the switch for the fan. The fan used to be connected to the light switch so it always came on when you turned the lights on. Now the fan has it's own switch is not used as much. Even though, I don't think this should make much of a difference if any.