Humidity in racks

hello i plan on building a snake rack pretty soon and i was wondering how i would be able to tell the humidity in the racks? or do i even need to worry about it in the racks?:8:

Use an accurite thermometer/hygrometer, once you get your rack set up, measure humidity in tubs, then add holes accordingly.

do i get the one with a probe and put it in each tub?or do i put it in a certan tub?

I only do one tub, because in a rack each tub will be basically the same :)