Understanding current density distributions (CDDs) in proton exchange membrane fuel cell (PEMFC) systems is critical in obtaining stable long-term system performances. This study elucidates the effects of the humidification temperature and clamping pressure on the CDD of a commercial-sized PEMFC, when the reactant gas is near saturation point. High-resolution CDDs of a single PEMFC were measured using a segmented current measuring board technique. The CDD results revealed that the humidification and current significantly affects the local current uniformity. When the cell voltage is higher than 0.65 V, the optimal humidification temperature must be higher than the cell operating temperature by 0-5 degrees C. This prevents membrane dehydration at the channel inlet region. When the cell voltage is lower than 0.65 V, the suggested humidification temperature must be lower than the cell operating temperature by 0-5 degrees C. This may reduce the possibility of flooding at the outlet regions of the flow channels. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.