Abstract: The widespread use of automatic weather stations has significantly improved the accuracy of meteorological monitoring, providing critical support for various applications, including forecasting and warning, meteorological services, climate analysis, and scientific research. This paper delves into an in-depth analysis based on the daily precipitation data collected from both national and automatic weather stations between 2015 and 2021. It explores the multi-scale spatial and temporal distribution of precipitation, as well as the characteristics of heavy rainfall in terms of spatial categorization and intensity, accompanied by a brief overview of the relevant weather backgrounds. The study yields several key findings: (1) A novel spatial classification index for heavy rainfall has been developed, which categorizes rainfall into four distinct types: local, partial, wide-range, and territory-wide. This classification considers the independence of assessment factors and the non-uniform distribution of rainstorm stations using area-density weights. Additionally, an assessment index for heavy rainfall intensity has been developed, considering the number of rainstorm stations and the disaster-causing effects of different rainfall magnitudes. By using the percentile method to determine the intensity grade of heavy rainfall, the spatial range and intensity of heavy rainfall are closely connected. (2) The city of Xiamen exhibits significant regional heterogeneity in precipitation, largely influenced by its unique topographic and geomorphological characteristics, including mountains, seas, bays, and urban areas. Notably, the mean annual precipitation and frequency of heavy rainfall tend to increase gradually from the coast to inland. Moreover, the occurrence of rainstorms is intricately linked to the topographical distribution. (3) Between 2015 and 2021, Xiamen experienced a total of 106, 37, 16, and 5 rainstorms categorized under the aforementioned classifications, respectively. Heavy rainfall occurred every month but was particularly concentrated in the main flood season from May to September, with peaks in June and August. The analysis identified 8 extremely heavy, 24 heavy, 33 relatively heavy, and 99 general cases of rainfall, with the highest total and average intensity recorded in 2016 and the weakest in 2020. Notably, the spatial categorization of the 8 extremely heavy events varied from wide-range to territory-wide, while the 99 general heavy rainfall events were local-range events. (4) The typical systems influencing the occurrence of regional torrential rains include warm–cold air activities, tropical cyclones, southerly streams, the northward uplift of convergence zone, low-level wind shear, and strong convection. Warm–cold air activities and tropical cyclones are particularly responsible for wide-range and territory-wide heavy rainfall events. A rare territory-wide heavy rainfall event occurred on Dec 9, 2015, triggered by the interaction of weak cold air and the strong, warm, moist airflow.