Abstract: Lakes, as heterogeneous underlying surfaces, exert significant influences on local thunderstorms and lightning activity because of their unique thermodynamic and hydrological characteristics. As a typical shallow lake in China, Lake Taihu is surrounded by complex underlying surfaces and therefore serves as an ideal region for investigating the effects of heterogeneous surfaces. Based on the World Wide Lightning Location Network (WWLLN) data from 2013 to 2018, this study identified thunderstorm activity using a Density-Based Spatial Clustering of Applications with Noise (DBSCAN), generating two sets of lightning clusters via two parameter configurations to identify thunderstorm activity and high-lightning-density areas over and around Lake Taihu. Combined with variations in lightning frequency and stroke energy along the propagation path, the spatial distribution, thunderstorm classification, typical movement paths, and diurnal variation characteristics of these thunderstorms were statistically analyzed. The results are as follows. (1) Lightning density in the Lake Taihu region generally exhibits a west-east decreasing pattern, with relatively high-value areas located along the western, northern, and eastern shores of the lake, as well as over the central-western lake surface. (2) According to the spatiotemporal characteristics of the lightning clusters, their parent thunderstorms can be classified into four types: lake-enhanced type (35.8%), western-shore dissipating type (8.1%), local type (55.5%), and merger-enhanced type (only 1 case). Significant differences exist among these thunderstorm types in the variation of lightning frequency and stroke energy after moving over the lake surface. Thunderstorms with relatively active lightning activity before entering the lake may be enhanced or maintained after moving over the lake due to lake effect, whereas weaker ones may gradually dissipate. (3) Most thunderstorms with clear path characteristics originate over the mountainous area to the west of Lake Taihu and then move eastward. If local thunderstorms initiated over the lake surface are also included, approximately 71% of thunderstorms exhibit an increase in lightning frequency or radiated energy over the lake surface. (4) Thunderstorm activity over and around Lake Taihu is mainly concentrated during daytime, with the peak lightning activity occurring from the afternoon to the early nighttime. Thunderstorms initiated over the lake surface at night are relatively few and are mostly local, short-lived thunderstorms, while lake-enhanced thunderstorms are mainly initiated from 11:00 BT to 15:00 BT and around 18:00 BT. These findings highlight the role of shallow lakes, represented here by Lake Taihu, in modulating thunderstorm activity. They may also provide useful guidance for lightning warning services in the Lake Taihu Basin and for thunderstorm studies in other lake-land interface regions.