<p>Climate change has increased precipitation variability and the frequency of extreme events, influencing the occurrence of drought hazards. Accurate and precise regional drought monitoring requires consideration of both spatiotemporal variability and extreme precipitation values. This study presented the Inter-Het Regional Drought Index (IHRDI), a novel regional drought assessment index based on the proposed integrated weighting scheme that accounts for interdependence and heterogeneity. Weights are computed using a Bayesian network model and the square deviation approach, addressing the issues of under- and over-representation in precipitation data across multiple meteorological stations. The IHRDI was applied to precipitation time series from five homogeneous regions in Pakistan and compared with the Standardized Precipitation Index (SPI) and the regional Seasonally Combinative Regional Drought Index (SCRDI). Evaluation using linear correlation, spatiotemporal plots, and other statistical measures showed that the IHRDI consistently exhibits a higher correlation with SPI than the SCRDI, outperforming both indices in capturing regional drought conditions over various periods and areas. A comprehensive analysis of drought severity, duration, and trends revealed significant variability in drought severity and duration, particularly at longer time scales. Further, the Mann–Kendall test indicated a significantly increasing trend in drought conditions across most regions and time scales, highlighting the growing vulnerability of the regions to extreme drought events, with intensity and duration increasing at longer time scales.</p>