Phase change material (PCM) coupled with night ventilation (NV) is regarded as a promising cooling strategy. The suitability of PCM coupled with NV in transition and hot seasons of 10 cities in Western China was investigated based on a non-air-conditioned office building. The optimum phase change temperature (PCT) and the cooling potential of PCM coupled with NV in transition and hot seasons were determined by numerical investigations using EnergyPlus. The results showed that the optimum PCT for the 10 selected cities varied from 23 degrees C to 29 degrees C. PCM coupled with NV was suitable for application in all of the selected cities, but the PCM strategy was the best choice for the transition season in cities in severe cold zone. Applying PCM coupled with NV strategy could reduce the discomfort hours in the transition season by at least 16% compared with NV alone. In addition, the favorable outdoor air dry-bulb temperature (T-out) for the application of PCM coupled with NV was obtained for the selected cities in Western China, which had the following characteristics: (1) the diurnal temperature difference (Delta T) exceeded 6.8 degrees C, (2) the average value (T-ave) was close to 27 degrees C, (3) the minimum value (T-min) was 2.7 degrees C lower than the optimum PCT and the maximum value (T-max) was 1.7 degrees C higher than the optimum PCT. (C) 2019 Elsevier Ltd. All rights reserved.