On March 15, some States and cities in India experienced the first of severe heatwaves for the year 2025. This was 20 days earlier than the first severe heatwave in 2024. In the last decade, the number of severe heat days and the severity/intensity of heatwaves have been rising. The year 2024 was the warmest year on record at about 1.55°C above pre-industrial level, according to the World Meteorological Organization. In India, December 2022 was the hottest December since temperature monitoring in the country started in 1901. The frequency of heatwaves in India has increased in the last two decades, in comparison to the previous two decades.
The impact of rising external temperature and heatwaves along with humidity and wind speed, is reflected in the form of heat stress. When the outside temperature reaches close to our body temperature of 37° Celsius, the body fails to release the internal heat which is generated as a part of the basal metabolic rate. Thus, one starts to feel heat-stressed. Heat stress can affect multiple organs including the kidneys, the liver and the brain, and may cause sickness and even death.
Socio-economic impact and equity issue
However, heatwaves have many non-health and socio-economic impacts. Climate change, specifically rising temperature, is one of the causes of farming sector stress in India. With rising temperatures, it becomes difficult for farmers to work in the field and harvest comes down. Livestock can die, further impacting the poor and farmers. Heat stress can reduce livestock production, food production, farm productivity and the ability of outdoor workers/ workforce productivity. As India is a labour-intensive country, especially in the agriculture and construction sector, heatwaves result in an individual’s reduced working ability. Thus, loss of work hours and loss of job reduce personal and family income. In India, up to 75% of the workforce, or 380 million people are dependent on heat-exposed labour. There are estimates that heat stress results in an economic loss of 3% to 5% of GDP in many countries including India. There are estimates that in 2023, nearly 6% of work hours in India were lost due to heat stress. As temperature rises, electricity demand and power cuts affect industrial production. Heatwaves and heat stress impact personal income and may slow down a nation’s economic growth.
Heat-related data indicate that the impact of heat stress is worst on the poor, the marginalised, migrants, subsistence workers, women, and the elderly. Women are additionally impacted due to social norms such as working in the kitchen, the need to wear clothing due to cultural requirements, or space allocated for sleeping. From every angle, it is a matter of inequity.
As early as the middle of the 19th century, researchers and scientists made observations that urban areas have a higher temperature than rural areas, arriving at the inference that much of the rise in temperature is human made. Yet, it took another 150 years for the first heat and health action plans (HHAP) to be prepared in the European countries; ironically, the first such efforts were from the non-tropical regions, between 2003 to 2008.
In 2013, Ahmedabad, Gujarat, became the first municipal corporation in Asia to develop a heat action plan (HAP). Since then, and in the last decade, more than 23 Indian States and around 140 cities across India have State- and city-level HAPs. India’s National Programme on Climate Change and Human Health (NPCCHH) also provides heat advisories and other health-related information through the National Disaster Management Authority (NDMA).
Heat action plans need nuances
Most HAPs have four to five components, i.e., early prediction of heatwaves to raise alerts; increasing awareness among the communities/people on actions to be taken; and preparing and getting the health system ready to manage health conditions. The fourth component of such plans focuses on ensuring long-term measures to reduce heat, government initiatives to increase the number of trees and parks and keeping gardens open for public use. There is experience, from various cities, about painting rooftops white to reflect heat. The fifth component of HAP must be collecting, analysing and interpreting heat stress, and also morbidity and mortality data. Though many Indian States and cities have HAPs, their implementation demands more attention. These HAPs have shown partial success and only in some settings where city authorities work with the State government, engage local public health institutions, subject experts, non-governmental organisations and community-based organisations.
As India might be heading into another warm year, there are some learning and action points which should be considered.
First, every State should consider developing and/or updating its HAP, informed and guided by the learnings and best practices from the existing plans. The HAP should factor in humidity and not just temperature. The HAPs should be developed based on a local vulnerability assessment. Plans should ensure the clear accountability and the responsibility of various identified stakeholders. These should be activated from the beginning of March.
Second, a review article published in the medical journal, Preventive Medicine: Research & Reviews, noted that most Indian cities have excess mortality due to heat stress, which demands better heat stress-related data collection. Besides, when heat-stress related data is not comprehensive and an under-estimation, it is worthwhile interpreting available data to review who the people who suffer a heat stroke are and which part of the city they live in, which, in turn, would provide useful, actionable and potentially lifesaving information.
Third, a few countries such as the United Kingdom have started Heat Health Alert (HHA) systems which use both daytime and nighttime maximum temperatures. The HAPs in India also need to factor in the day and nighttime temperature monitoring. There is also a need for more sophisticated and specific warning systems which can predict thermal comfort and the timings during the day when temperatures are likely to be low. This can ensure health as well as continuity of work such as school and office functioning.
Fourth, the long-term preventive measures of HAPs need to be strengthened. Better building and urban infrastructure and building material need to be promoted. Heatwaves impact the poor the most, and it is during these periods that governments should also consider financial support for informal sector workers who may suffer wage losses.
Fifth, a 2022 study from three Asian countries (India, Pakistan and Bangladesh) suggested that the universal ‘stay indoors’ advisory during specific hours may not be helpful for all families. People in a poor neighbourhood and in a confined space that is surrounded by high-rise buildings may experience higher temperatures in their homes and outside, in comparison to the rest of the city. Even within cities, there is a need for geography and social context-specific heat advisories.
Need for a people-centric approach
Sixth, it is time that more Indian cities start ‘summer or cold shelters’ similar to winter shelters. There are already some States that are developing a ‘cool roof policy’ to promote the use of material in building roofs which will keep houses cool by reflecting sunlight. Prevention of heatwaves needs more practicable and science-based innovations.
Seventh, during heatwaves, local authorities carry out a lot of short-term measures such as advisories to drink a lot of water. However, to make that happen, municipalities and city authorities need to ensure the easy availability of drinking water points, and the availability of electrolyte solution/ORS powder. Offices and workplaces (both formal and informal) should allow staggered work times and also early morning and late evening work. Work can be closed during the day, especially for those who work in the informal sector and open spaces.
The evidence is that investments in heat-related actions and adaptation are highly cost effective. Therefore, every effort should be made to reduce the economic burden of heat stress in hospitals and emergency rooms and its indirect social and economic costs. With every passing year, in India and globally, the average temperature is rising. Therefore, the actions should be focused not just on short-term measures but also on long-term strategies to address the challenge of rising temperatures and steps such as enhanced coordination between multiple agencies, with inter alia initiatives such as provision of insurance coverage for lost work days. If policymakers and planners remember that a heatwave is an equity issue and that the approach has to be people-centric, half of the task will be done.
Dr. Chandrakant Lahariya is a practising physician and expert in global health, with nearly 17 years of professional work experience with the United Nations system including the World Health Organization and UNICEF
Published – April 21, 2025 12:16 am IST