The enhanced severity and frequency of extreme weather events, such as combined heat waves and heavy rainfall, pose significant concerns due to their devastating regional impacts. This research quantifies the association between heatwaves and heavy rainfall events using Event Coincidence Analysis during 1951-2020. We compute both the Precursor Coincidence Rate (PCR) and the Trigger Coincidence Rate (TCR), which are key metrics in understanding the physical link between heatwaves and subsequent heavy rainfall events. The PCR indicates the proportion of heatwave events that precede heavy rainfall events, providing insight into the reliability of the precursor (heatwave events) as an indicator of the trigger event (heavy rainfall events). TCR represents the proportion of heavy rainfall events that follow heatwave events, useful for evaluating the predictive power of the precursor. Our results reveal TCR decreased in the recent period as compared to the base period for shorter time frame (temporal windows ΔT=2 and Delta ΔT=5), however, exhibited a notable rise (50%) observed in approximately 70% of the grid points for longer temporal windows ( ΔT=7). The observation is very well in congruence that the moisture holding capacity of the atmosphere has enhanced and convective activity and latent heat release (heatwave producing extreme rainfall) take longer than usual. Moreover, PCR increased for all temporal windows, indicating an increased probability of heatwaves triggering precipitation events within 7 days of their end and predictive potential in the recent period compared to the base period. Approximately 27% of grid points experienced one heat-wave event within 7 days prior to heavy rainfall occurrence in the recent period, compared to 13% in the base period, for every 5 precipitation events. Results indicate an increased coupling between the occurrence of heat waves and heavy rainfall within a very short period, attributed to moisture convergence and atmospheric convection.
