Heatwaves in India: Understanding the Threat and the Way Forward

As summer temperatures climb across India, the threat of heatwaves looms large. A heatwave is qualitatively a condition of air temperature that can prove fatal to the human body upon exposure. Quantitatively, it is defined by temperature thresholds for a region, based either on actual temperatures or their departure from normal. Some countries also use a heat index that factors in humidity, or rely on extreme percentile thresholds.

In India, the India Meteorological Department (IMD) specifies that a heatwave is considered only when the maximum temperature reaches at least 40°C for plains and 30°C for hilly regions. When the normal maximum temperature is 40°C or less, a departure of 5-6°C from normal constitutes a heatwave, while a departure of 7°C or more is classified as a severe heatwave. Heatwaves typically occur between March and June, occasionally extending into July.

Several conditions favour their formation: the presence of hot, dry air transported over a region, absence of moisture in the upper atmosphere, a practically cloudless sky, and large-amplitude anti-cyclonic flow.

The health impacts are severe, ranging from dehydration and heat cramps to heat exhaustion and heat stroke. Children, the elderly, and those with pre-existing conditions are especially vulnerable. Workers such as vegetable vendors, cab drivers, construction workers, and police personnel face heightened risks due to prolonged exposure.

India is witnessing more frequent heatwaves due to urban heat island effects, where paved and concrete surfaces and lack of tree cover make temperatures feel 3-4 degrees higher. Globally, rising average temperatures and climate change are leading to higher daily peaks and longer, more intense heatwaves.

The government has launched several initiatives to combat climate change, including the National Action Plan on Climate Change (NAPCC), the International Solar Alliance, the FAME scheme for e-mobility, AMRUT for smart cities, the Pradhan Mantri Ujjwala Yojana, the UJALA scheme for LED bulbs, and the Swachh Bharat Mission.

Looking ahead, experts suggest developing localized climate risk atlases, identifying heat hot-spots through meteorological data, and implementing local Heat Action Plans with inter-agency coordination. Reviewing occupational health standards, promoting traditional adaptation practices, and popularising simple design features like shaded windows and insulating materials are also recommended. Policy coordination across health, water, and power sectors is essential, along with democratizing climate data and investing in R&D. Ultimately, addressing climate change requires treating it as a developmental challenge, not just an environmental one, and securing global cooperation, especially from major emitters, to achieve net-zero emissions.