Generally, the humidity in the bator is what matters, however, with a very dry climate, you may have to add water more than someone in the sticky south, where some folks may not have to add water at all, or just a couple drops on occasion. The reason for that is that the air from the surrounding environment is drawn into the bator through the air inlets. If that air is very dry, you will find you have to add water more often than if that air is soupy. Does that make sense?