Heatwave Hazard in Ahmedabad, India: How Close Are We to Another May 2010 Crisis?

Heatwaves pose an escalating threat to urban populations, particularly in rapidly expanding cities like Ahmedabad having population nearing to 10 million, where rising temperatures and urban heat island effects intensify heat stress. In May 2010, an unprecedented heatwave led to approximately 1,344 fatalities within a matter of days, underscoring the lethal consequences of extreme heat events. As climate change continues to drive up global temperatures, evaluating the recurrence, severity, and spatial variability of such extreme events is crucial for urban resilience and disaster preparedness.

This study assesses the current heatwave hazard in Ahmedabad by comparing the ambient temperature and heat index of May 2010 with those of May 2024. We employed the Weather Research and Forecasting (WRF) model at a high spatial resolution of 1 km × 1 km to simulate hourly ambient temperatures for both time periods. We validated the simulated temperature and relative humidity for May 2024 against field observations from three monitoring locations. The model demonstrated excellent agreement with observational data, yielding a Pearson correlation coefficient (r) of 0.96 for T-2 (ambient temperature at 2 m height) and 0.85 for relative humidity (RH), confirming the high reliability of our simulation approach.

Using NOAA guidelines, we calculated the heat index at an hourly scale for each grid point across Ahmedabad, integrating both T-2 and RH to assess the intensity of heat stress. By mapping the spatial distribution and occurrence frequency of heat index ranges, we examined whether the thermal conditions of May 2024 exceeded the deadly thresholds recorded in May 2010 or exhibited signs of mitigation. Our comparative analysis highlights critical trends in the progression of heat stress and exposure patterns within the city.

As heatwaves become more frequent and intense due to global climate change, such assessments are indispensable to enhance a city’s resilience against future heatwave crises.