Yes the average humidity in your region is a factor definately and also more micro climates in a larger tank but even smaller tanks are going to have near 100 percent humidity usually in a dark spot or even 1 inch throughout the tank above the substrate...assuming the substrate is atleast kept moist, since the evaporated moisture is more concentrated at or just above the point of evaporation, then disperses.
So this means u may have to mist more frequently when your tanks have alot of ventilation...but mainly the point i was trying to make was that alot of people seem overly concerned that their frogs are going to die or something if the whole tank isnt at a constant 80% humidity or above.
Good ambient Humidity through frequent enough misting is definately key to seeing your frogs....or atleast having a small water feature... i've noticed that my frogs even when they were kept in tanks with lower ambient humidity and only misted once or twice a day would be out and about quite abit if they had a water source to "recharge" at periodically then off they'd go.... you can have a small water bowl even...and in such cases i usually put java moss and/or salvia natens in the water bowl to filter the water and that allows me to just top it off as needed instead of emptying it often....small feeder guppies and other tropical fish can even live in such a small water feature if filtered with plants. ofcourse in a 10 gal you'd have to sacrifice quite abit of floor space for a bowl, so thats why i like the waterfalls like the exoterras, cuz its still a place the frogs can climb on even when not in the water.
Everything I've ever written is/was just my opinion!