Study region: The Kanto region, Japan. Study focus: Detailed assessment of present and future climate conditions and their effects on water resources in the Kanto region of Japan using a modified pseudo global warming dynamical downscaling method with a numerical weather prediction model. New hydrological insights: In future climate conditions, results on the change in annual precipitation are scattered, with significant variations in mean annual precipitation and the standard deviation in very limited areas. In contrast, minimum annual precipitation is found to decrease and years with low rainfall to be more frequent. During the drier summer season, the minimum accumulated rainfall is expected to become smaller across a wide region in the future. In addition, frequency distributions of future daily precipitation show a decrease of weak precipitation and an increase of heavy precipitation. Such variations are unfavorable for water recharge and indicate that water resources management will become increasingly difficult in the future because of global warming. The lower rainfall conditions are due to the lower relative humidity, more frequent stable stratifications and sub-synoptic atmospheric conditions leading to higher-pressure anomalies around Japan.