Threshold determination and temperature trends analysis of Indian cities for effective implementation of an early warning system

Extreme heat events (EHEs) have been linked to increased mortality rates, rendering them a valuable research topic in both climate and public health. Early warning systems are highly impactful in prevention and management of heat-related illnesses. We aimed to determine the preliminary maximum temperature thresholds for Nagpur and Rajkot city of India by analyzing the meteorological and mortality data to enable the heat-health response system based on the heat wave disaster risk of a particular state and city. We conducted a trend analysis with daily maximum temperature and all-cause mortality data of Nagpur and Rajkot (2003-2017) cities, also city-specific thresholds evaluated for both cities. There was a significant association between all-cause mortality and extreme heat events and it was more profound when temperatures were above 40.1 degrees C, but V-shaped relationship of mortality-temperature was noted only for Nagpur city. The dose-response relationship between maximum temperatures and deaths alert thresholds to activate heat health response for red alert set at 46 degrees C and 44 degrees C for Nagpur and Rajkot city respectively. This study suggests that determining local thresholds is important for developing and implementing scientific early warning systems to prevent heat-related illnesses.