A heatwave is more than just a spike in temperature; it's a condition that becomes perilous for human health when exposed. Quantitatively, it's defined by specific temperature thresholds over a region, often in terms of actual temperature or its departure from normal. In some countries, including India, it's characterized by criteria such as the heat index, based on temperature and humidity, or extreme percentiles of temperatures.

According to the Indian Meteorological Department (IMD), in India, the criteria for declaring a heatwave include a maximum temperature of at least 40°C for plains and 30°C for hilly regions, or a departure from the normal temperature of 4.5°C to 6.4°C, with severe heatwaves declared for departures exceeding 6.4°C. Additionally, warm nights, when minimum temperatures remain high, further compound the issue.

The recent report from the IMD advisory signals concerning temperatures above normal in April to June highlights the pressing issue of heatwaves. Several states, including Madhya Pradesh, West Bengal, Maharashtra, Gujarat, and Andhra Pradesh, already experienced temperatures ranging from 40°C to 42.6°C in the past week.

IMD's forecast indicates a warm April-June period, with high probabilities of prolonged heatwave episodes, particularly affecting states like Rajasthan, Gujarat, Maharashtra, Odisha, North Karnataka, Andhra Pradesh, and Telangana. These forecasts come amid continued warm conditions attributed to factors like El Niño.

Economy sizzles 

The economic ramifications of such extreme weather events are significant. Higher temperatures lead to increased evaporation, exacerbating water scarcity issues, particularly concerning as water capacities across the country are low. Sectors like power, agriculture, and industry face challenges due to heat waves, paralysing productivity and output.

In agriculture, the backbone of India's economy employing over half of the population, heatwaves can cause crop damage, reduce yields, and strain irrigation water supplies, potentially leading to high inflation and food shortages. Labour-intensive industries also suffer from increased absenteeism and productivity losses.

Moreover, the energy sector faces challenges in meeting heightened power demand during hot weather, necessitating maintenance deferments and additional measures to ensure uninterrupted supply.

The recurrence and severity of heatwaves underscore the urgency for adaptation and mitigation strategies. The World Meteorological Organisation's (WMO) report on the state of the global climate highlights the escalating frequency and intensity of extreme weather events worldwide, including heatwaves, with profound socio-economic implications.