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The hourly precipitation data from the densified automatic stations over Hainan Island from April to September between 2017 and 2021 and the fifth generation global reanalysis data of the European Centre for Medium-range Weather Forecasts (ECMWF) with an interval of 1 h and a spatial resolution of 0.25°×0.25° are used to classify the circulation configuration of short-term heavy rainfall over Hainan Island. Furthermore, the synoptic diagnostic analysis method is used to synthetically analyse the environmental fields and physical fields of the short-term heavy rainfall processes, and the characteristics of the temporal and spatial distribution, circulation situation, and key environmental parameters of the short-term heavy rainfall over Hainan Island under various weather patterns are analysed. The results show that: (1) The short-term heavy rainfall over Hainan Island has an obvious diurnal variation characteristic, showing a single peak type, mainly occurring from 15:00 to 19:00. (2) The circulation patterns of short-term heavy rainfall over Hainan Island mainly include the South China Sea Trough, the South China Coast Trough, Southwest Trough, and cold front pattern. (3) The South China Sea Trough, South China Coast Trough, Southwest Trough, and cold front pattern account for 37%, 31%, 16%, and 16%, respectively. The cold front pattern mainly appears in April and May. The South China Sea Trough and South China Coast Trough mainly appear in July, August, and September, and the Southwest Trough may appear in other months except September. (4) The spatial distribution of short-term heavy precipitation varies significantly under different weather patterns. The South China Sea Trough type high-frequency stations are mainly concentrated in the northeast inland of Hainan Island, while the South China Coast Trough type high-frequency stations are mainly concentrated in the northern inland and western parts of Hainan Island. The Southwest Trough is mainly concentrated in the area north of Wuzhishan; the cold front pattern mostly occurs in the northern region of Hainan Island. (5) The humidity conditions of the South China Sea Trough and the South China Coast Trough patterns are good, with a high amount of unstable energy and weak vertical wind shear. The unstable energy for the Southwest Trough is high, with the humidity condition being average and the vertical wind shear weak. The cold front pattern has an obvious characteristic of being drier above and wetter below, and the wind speed difference (0～6 km) is the largest, with 75% quantile greater than 10 m/s. However, the unstable energy of the cold front pattern is the lowest.