Land–atmosphere interactions are fundamental processes in monsoon dynamics. This study, utilizing a novel causal analysis, reveals that soil moisture significantly influences surface air temperature across monsoon regions, intricately linked to the seasonal monsoon cycle. Furthermore, this research illustrates a strong connection between soil moisture and the occurrence of extremely hot days in pre-monsoon periods under conditions of depleted soil moisture and intense insolation. The proposed approach for measuring land–atmosphere coupling deepens our understanding of these interactions and contributes to enhancing forecast capability in monsoon regions, thereby strengthening resilience in vulnerable and densely populated monsoon regions facing threatening heat extremes in a changing climate.