Abstract: To investigate the necessity of high-resolution air–sea–wave coupling for improving short-term numerical weather prediction, a coupled air–sea–wave model consisting of ROMS (Regional Ocean Modeling System), WRF (Weather Research and Forecast model) and WW3 (WAVEWATCH Ⅲ) is established, and a set of sensitivity experiments is conducted. The Meiyu rainfall events from June 2023 are selected. We analyze the spatiotemporal characteristics of coupling effects on the precipitation and related meteorological fields. The results demonstrate remarkable spatiotemporal heterogeneity in atmospheric responses, including precipitation, 2-m air temperature, 10-m wind field, and specific humidity. Coupling-induced differential signals exhibited landward propagation, with localized differences in heavy precipitation reaching 10 mm (3 h)⁻¹ within 36 h and extensive differences in daily precipitation exceeding 50 mm d⁻¹ over regional scales within 3 days, in the land surface. Near-surface temperature and wind field differences reached 10% of the background values within 36 h. Vertically, the coupling effects on the wind and moisture fields propagated upward progressively and quickly with forecast time. The wind field response propagated faster than moisture variations, with differences penetrating the entire troposphere (up to 100 hPa) and covering the study domain within 36 h. Vertical velocity deviations triggered low-level dynamic adjustments that accelerated moisture vertical transport. Furthermore, the coupling effects induced discernible adjustments in the atmospheric circulation patterns of 7 days, with substantial geopotential height differences over land-based vortex systems at 500 hPa. This study confirms that air–sea–wave coupling considerably affects atmospheric element predictions along China’s southeastern coast within 36 h while nonnegligibly modifying the circulation patterns. The implementation of air–sea–wave coupling proves essential for enhancing short-term weather forecasting in Southeast China.