No such thing, silly name earner.
Detroit is humid enough not to be hard on pianos. Arizona is.
If Arizona wants a musical cultural center with pianos, it has to put special humidifiers in its pianos if it doesn’t want them to go forthwith to hell.
But it’s still relative. The humidity in Arizona is not literally zero. Cacti manage to live there that wouldn’t in the middle of the Sahara.
BWAHAHAHAHAH
You’re taking this position all the way to saying there is no such thing as objectively humid?! BWHAHAHAHAHAHA Is there also no such thing as UP?! BWAHAHAHAHA
Man you’re funny. Like a drunk on a staircase.