The potential distribution of ferroelectric domains on a (001) BaTiO3 single crystal surface was investigated via scanning Kelvin probe microscopy at room temperature, with and without an electric field applied parallel to the (001) surface. A reversal of the c domain charge was observed after reaching a critical electric field intensity of 6 V/mm, which was much lower than the 200 V/mm coercive field. An immediate recovery was observed upon switching off the electric field. The humidity has a significant effect on the intensity of the inversion electric field. Surface adsorbates significantly affected the ferroelectric surface potential behavior. Due to a low 4 kJ/mol desorption energy, the electric field successfully removed surface adsorbates, allowing for the surface potential to reflect the actual domain polarization state.