Lightning-induced fires represent one of the most critical hazards in chemical and petrochemical storage tank farms, particularly for floating-roof oil tanks (FROTs). Enhancing the lightning protection performance of FROTs requires a detailed understanding of their electromagnetic response to indirect lightning strikes. Inductive effects associated with nearby lightning events can lead to unintended operation of above-ground storage tank equipment and pose serious threats to operational safety. In this study, the electromagnetic effects of indirect lightning strikes on floating-roof oil tanks are investigated using a time-domain numerical approach based on the Transmission Line Modeling (TLM) method. The lightning current waveform is represented by the Heidler function to accurately characterize lightning strike parameters. The spatial distribution of electromagnetic field strength (EMFS) and power loss density (PLD) on the tank structure is numerically simulated and analyzed. Furthermore, a parametric sweep technique is employed to evaluate the influence of structural parameters on the electromagnetic response of the tank. This systematic approach enables an efficient and accurate assessment of lightning-induced effects and provides insights into the optimization of lightning protection measures for floating-roof oil tanks. Results indicate that the presence of shunts and bypass conductors in sufficient quantity can significantly reduce the electromagnetic effects resulting from indirect lightning strikes.