Abstract: Up to now there is no study on thunderstorm climatology based on long-term hourly observations over mainland China. Using hourly thunderstorm observations collected at 796 national-level stations during 1971—2010, the temporal and spatial evolution and duration characteristics of hourly thunderstorms over China are revealed, and some new findings are obtained. Over China, the spatial distribution pattern of annual average thunderstorm hours is close to that of annual average thunderstorm days. However, the situation is different in the Qinghai-Tibet Plateau, where the number of annual average thunderstorm days is high but the number of annual average thunderstorm hours is low, indicating that the duration of convective activity is shorter than that in the plain area. It is also found that the annual relative variability in areas of high annual average thunderstorm days and hours is significantly lower than that in areas of low annual average thunderstorm days and hours. Among the four seasons, the number of annual average thunderstorm hours in winter is the smallest, and many thunderstorms occur in the first half of the night. They account for the largest proportion of thunderstorms in the whole day. Nocturnal thunderstorms occur most frequently in summer, but their proportion of the thunderstorms in the whole day is the lowest. Nocturnal thunderstorms in Sichuan Basin are significant all year round. The diurnal peak of thunderstorm hours at each station mostly occurs in the afternoon and the trough largely occurs in the morning, and there are more thunderstorm hours in the first half of the night than in the second half. Affected by the East Asian summer monsoon, over most parts of China to the south and east of the Hu Huanyong line, the number of thunderstorm hours per thunderstorm day is not less than 3 h, whereas the number is significantly less than 3 h to the north and west of the Hu Huanyong line. For thunderstorms of different durations, thunderstorms that can last for 2 h occur most frequently over China and over different regions. The decadal variations of thunderstorm hours over China and over different regions all show a decreasing trend, but nocturnal thunderstorm hours have increased significantly since 2000. The significant decrease in thunderstorm hours in China is mainly due to the significant decrease of thunderstorm hours in the afternoon, and the increase in thunderstorm hours since 2000 is attributed to the increase in thunderstorm hours at night.