Water shortages in China have hindered development of mega cities, especially Beijing. Assessing the impact of temperature and precipitation on water resources is important. This study analyzed spatiotemporal variations and impacts of temperature and precipitation on water resources in Beijing from 1956 to 2013, using statistical and spatial analysis. The results showed the following. (1) Temperature and precipitation affect water resources variously from region to region; their correlation in mountains is lower than in other areas. Precipitation redistribution caused by terrain reduces water resources. (2) The inter-annual variabilities of precipitation, temperature and water resources are different among five water resource divisions. Because of ‘rain-slope’, Beisanhe's precipitation is larger than others; Yongdinghe's precipitation is less than others due to ‘rain-shadow’; suffering from urban heat island effect, Beisihe and Daqinghe-plain's temperature is higher than others; Beisanhe and Beisihe's water resources are greater than others due to area differences. (3) Water resources are positively correlated with precipitation and negatively with temperature. (4) In recent years, precipitation and water resources decreased and temperature rose. Population growth, land use/land cover change, urbanization and pollution affected precipitation, temperature and water resources. Imported water cannot completely solve water shortages. With increasing water demand, precipitation and temperature will significantly influence water resources in Beijing.