Rapid amplification of Compound Drought and Heatwave risk over India: a regime shift from arid northwest to humid southern and eastern hotspots

Abstract. Quantifying the regional intensification of Compound Droughts and Heatwaves (CDHW) is critical under changing precipitation regimes. The spatiotemporal evolution of CDHW events is investigated across India (1951–2016) using the Standardized Net-Precipitation and Distribution Index (SNEPI) to capture intra-monthly precipitation spell variability. Results indicate a statistically significant 86 % rise in the frequency of individual heatwaves and a significant drought intensification in historically humid zones. Consequently, the spatial extent of India affected by the CDHWs expanded from 10 % to 35 %, with hotspots transitioning from the historically arid northwest to humid eastern and southern regions. While lower-intensity CDHW events expanded 3 to 5 times spatially, the extreme category experienced a 25-fold increase. Notably, 46.4 % of moderate and 43.3 % of elevated events escalated to higher severities, suggesting a cascading amplification of risk. Despite intervening wet periods, 10 %–16 % of CDHWs recurred, indicating limited mitigation over traditionally wet and resilient regions. Agricultural impact analysis reveals that high-intensity CDHW years reduced national rice yields by 12.1 %, while wheat yields increased by 13.9 %, highlighting the critical but often overlooked influence of CDHW occurrences on India's major crops, i.e., suppressing water-sensitive rice production but favouring heat-resilient wheat cultivation. Furthermore, the emergence of statistically distinct new hotspots, particularly in Kerala and Assam, coincides with a 4–10 fold increase in exposed urban populations, underscoring the urgent need to reassess regional adaptation strategies under evolving rainfall regimes across both traditionally arid and humid zones.