Memristors based on anionic-electronic resistive switches represent a promising alternative to transistor-based memories because of their scalability and low power consumption. To date, studies on resistive switching have focused on oxygen anionic or electronic defects leaving protonic charge-carrier contributions out of the picture despite the fact that many resistive switching oxides are well-established materials in resistive humidity sensors. Here, the way memristance is affected by moisture for the model material strontium titanate is studied. First, characterize own-processed Pt|SrTiO3-|Pt bits via cyclic voltammetry under ambient conditions are thoroughly characterized. Based on the high stability of a non-volatile device structures the impact of relative humidity to the current-voltage profiles is then investigated. It is found that Pt|SrTiO3-|Pt strongly modifies the resistance states by up to 4 orders of magnitude as well as the device's current-voltage profile shape, number of crossings, and switching capability with the level of moisture exposure. Furthermore, a reversible transition from classic memristive behavior at ambient humidity to a capacitively dominated one in dry atmosphere for which the resistive switching completely vanishes is demonstrated for the first time. The results are discussed in relation to the changed Schottky barrier by adsorbed surface water molecules and its interplay with the charge transfer in the oxide.