I've got 2 vent holes I can plug w/ small corks (I've been concerned about oxygen so I have them both open),
the weirdest part is we have had torrential rain, like literally over 6 inches in the past 24 hrs at my house,
and the acu-rite indoor/outdoor thermometer/hydrometer (outdoor remote IN bator) is telling me my house is 51% while the bator is 44% , so except for needing the heat, I'd be better off humidity wise to just leave the lid off entirely. I really did NOT expect this situation (cooler bator currently has 2 containers w/ water, 1 w/ a sponge inserted partway out the top like a wick, & I'd think the hydrometer was just plain wrong, but then I saw how totally DRY last night's wet washcloth is, it was dripping w/ hot water when I tossed it in about 20 hrs ago).