More frequent high temperature extremes caused by climate change may significantly increase urban water demand and consequently the vulnerability of urban water distribution systems (WDSs). A methodology was developed to quantify the impact of high temperature extremes on urban water demand and WDSs by integrating the methods of climate analogy, end use modeling and WDS hydraulic simulation. A case study on a new development area in Beijing showed that high temperature extremes could lead to an increase in total water demand by 5.7%, equivalent to an increase in per capita daily water demand by 19.83 L, as compared with normal summer. Furthermore, significant increases in water demand were found during morning and evening peak hours, which caused the failure of another 13 percentage points nodes of the WDS to meet the pressure requirement of 28 m.