I’ve seen people set up a system that bleeds a small amount of hot water into the line that fills the toilet tank to keep it up to room temperature or thereabouts. The idea is to prevent condensation on the outside of the tank.
Humidity that high is a non-issue here. This morning it's 67%. In the summer it's usually below 20%. The water comes out of our well at about 58F year round. That's not too far below room temp.
