The India Meteorological Department (IMD) has sounded the alarm on heatwave conditions, initially observed in isolated pockets of west Rajasthan since March 27, 2024. However, a broader swath of regions is expected to confront humid heatwaves in the days ahead. IMD’s criteria for identifying a heatwave involve temperatures surpassing 40°C in plains, 37°C in coastal areas, and 30°C in hills. Additionally, when temperatures soar above 45°C, a heatwave is promptly declared, irrespective of deviations from normal temperatures. Notably, this classification overlooks relative humidity, a key factor contributing to humid heatwaves. To address this, the concept of wet bulb temperature or heat index has gained significance, with a consensus on safe levels below 30°C and extreme danger above 35°C, where human fatalities become highly probable. The IMD has introduced new terms to describe heat stress, including ‘warm night conditions’ and ‘hot humid weather’, as part of efforts to enhance public awareness and preparedness.
