Heatwaves are characterized by hot weather and higher than normal daily temperatures that can last for a few days to months. Heatwave events are on the rise; many parts of India are facing more frequent, intense and longer-lasting heatwaves. Heatwaves have also become one of the deadliest forms of extreme weather events. As per official figures, 3,798 people lost their lives due to heatwaves in India between 2018 and 2022.
According to a report by the National Programme on Climate Change and Human Health, 48,156 suspected heatstroke cases were reported in 2024 and there were 269 suspected and 161 confirmed heatstroke deaths. The actual toll may be higher due to underreporting, delayed health effects and because heatwave deaths are difficult to assess. The Intergovernmental Panel on Climate Change, an international scientific body, has long predicted that heatwaves will intensify in the future. As per their assessment, human activities have more than doubled the probability of heatwave events in some regions. According to a 2022 note by the World Meteorological Organisation, the 2022 India-Pakistan heatwave was “30 times more likely” due to climate change. Such predictions have become a reality and climate change-induced heatwaves are frequently affecting cities and rural communities. Heatwaves, accompanied with elevated atmospheric carbon dioxide levels, are impacting agriculture and reducing crop yields.
Their direct impact on humans is more pronounced in urban areas which have high vulnerable populations. A heatwave is a public health hazard, and no part of India is untouched from this threat. Heatwaves in urban areas, which already experience an urban heat island effect, are a double whammy for the citizens. Cities in developing countries like India are known for their concrete surfaces, dense population and grey infrastructure, reducing green cover and heat-trapping activities. They are home to millions of residents who often live in close quarters; habitations include slums and other low-income settlements with poor ventilation, no green cover and limited access to cooling. While everyday heat can be managed with measures like fanning or being in shade, such measures are inadequate during a heatwave event especially when humidity drives up the “heat index.” In such a scenario, the air feels much hotter even at normal temperatures, and it is harder for the body to cool itself. The “heat index” combines the temperature and humidity conditions for an area, and ideally a few other factors, to determine how hot it actually feels.
The resulting “feels like” temperature can be very different from the actual temperature. The Delhi Heat Action Plan 2024-25 explains this further: “if the air temperature is 34°C and the relative humidity is 75%, the heat index – how hot it feels – is 49°C. The same effect is reached at just 31°C when relative humidity is 100 per cent.” Relative humidity is the percentage of water vapour in the air relative to the maximum it can hold at that temperature. It is important to include this “feels like” or apparent temperature, in addition to the actual temperature, when sending out localized heatwave alerts. Heatwaves in urban areas are concerning not only because of high population density, but also because of millions of gig and informal workers who spend long hours outdoors.
This large urban work force – comprising delivery executives, cab drivers, and street vendors – is directly exposed to extreme heat without adequate protection. Traditional employment offers some protection such as breaks and rest periods, health insurance and other safety protocols. Gig workers do not enjoy any such safeguards. Corporate responsibility towards gig partners may help in some cases, but for others not working during peak heat is a difficult choice between risking their health or their livelihoods. Existing heat action plans fall short on this parameter which requires urgent government intervention. Many urban local bodies are preparing and implementing heat action plans. All such planning must begin with identifying and categorizing the more vulnerable groups in urban areas.
This will ensure no group is left behind and help is provided in other ways such as identifying locations for installing cooling shelters and similar infrastructure. Integrated approaches for heat adaptation are also needed, e.g. each urban centre must protect its green areas and adopt green infrastructure (GI) in urban development. GI is a nature-based solution which includes street trees, vertical gardens, green roofs and waterways. Heatwaves occur during summer when water is a scarce resource and is also needed for cooling. Water conservation through rainwater harvesting and reviving ponds and baoris (stepwells) will help mitigate heat stress while also enhancing urban resilience.
Traditional architecture must also be revived in urban planning, especially elements like chajja (overhangs), jaalis (perforated screens) and courtyards which were inherently designed to enhance comfort in hot climates. Heatwave adaptation solutions are many and within reach, what is lacking is serious top-down policy and integrated planning for effective implementation.
(The writers are, respectively, an associate professor and a student at the Jindal School of Environment & Sustainability, O.P. Jindal Global University, Haryana, India.)
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