India is already reeling under extreme heat this year. The India Meteorological Department (IMD) issued its first heat wave alert on April 7, 2025, forecasting above-normal temperatures across the country from April to June. Heat waves, hot and humid conditions, and warm evenings began early this year in numerous Indian states. February was the hottest in 125 years, with an average mean temperature of 22.04°C—also the driest, receiving less than half the usual rainfall.
Between February 11 and 23, 2025, 31 states and union territories (UTs) saw nighttime temperatures at least 1°C above normal at least once. Of them, 22 states/UTs recorded night temperatures 3°C to 5°C higher than typical. According to the Intergovernmental Panel on Climate Change's (IPCC) Sixth Assessment Report, heatwaves in India will become more frequent in the future.
What are heat waves?
A heat wave is a prolonged period of unusually higher temperatures than what is normally expected over a region. The IMD has a network of observatories in different parts of the country that collect and monitor these changes in temperatures along with relative humidity, pressure, wind speed, and direction.
They declare a heat wave when:
The maximum temperature of a place reaches ≥ 40°C in plains, ≥ 30°C in hilly areas, and ≥ 37°C in coastal regions, with deviations ≥ 4.5°C from normal.
A severe heat wave is declared if temperatures are ≥ 6.4°C above normal or reach ≥ 47°C.
The actual maximum temperature reaches ≥ 45°C, while a severe heat wave is declared when the actual maximum temperature is ≥ 47°C.
Criteria must be met for at least two consecutive days at two monitoring stations in a meteorological subdivision.
IMD has also introduced a Heat Index, —an experimental tool that factors in humidity to assess human discomfort and provide early guidance.
Warnings for heat waves
The India Meteorological Department (IMD) issues warnings based on colour codes that indicate the severity of the heatwaves to alert relevant officials and the disaster management authority for necessary action. The four colour codes include Green - No action needed; yellow—Watch and stay updated; orange—Be prepared. red - Take action.
What is causing heat waves in India
India witnessed an exceptionally dry winter this year. This, combined with a weakening La Niña phase, warm easterly winds and increased greenhouse gas emissions, are leading to this unusual rise in temperatures this year
Heat waves can impact water availability, food production, biodiversity and health
Heat waves can lead to drought-like conditions by accelerating evaporation and reducing soil moisture levels. Decreased rainfall during heat waves can lead to water scarcity and restrict availability of water for human consumption. Heat wave induced water scarcity can also impact agricultural production, livestock, poultry and fisheries production
India has been identified as one of the top countries that will experience the most significant increase in the gap between water availability and demand under warming scenarios. This will not only impact food production but will also impact the health of populations.
Extreme heat can trigger deaths and disease
Exposure to extreme heat can lead to heat cramps, heat exhaustion, heatstroke, and hyperthermia and also deaths and hospitalisations in extreme cases, especially among the vulnerable, such as the old, poor, and those with preexisting health conditions.
Evidence from north-central India, Ahmedabad, Hyderabad, Maharashtra, and Surat shows that deaths have increased by 33.3 percent, 43 percent, 57 percent, 33 percent, and 20 percent, respectively, when temperatures have reached ≥40°C.
Heat waves can lead to rise in infectious diseases
A warmer climate can lead to favourable conditions for bacterial growth in food and water, triggering diseases such as diarrhoea, cholera, infective gastroenteritis, dysentery, and malnutrition that can spread to others due to the shortage of clean drinking water and poor hygienic practices.
Heat waves can make people vulnerable to communicable diseases
People exposed to high heat can suffer from recurrent dehydration, making them vulnerable to cardiovascular diseases, cancers, respiratory issues, heat stroke, and chronic kidney diseases. Extreme temperatures can also cause cardio-pulmonary mortality problems due to allergens and pollutants, as heat can lead to stagnant conditions trapping pollutants in the air.
High temperature can affect mental health
Dr. Vikram Gupta, a public health expert and a doctor, says, “As temperatures rise, so does our mental vulnerability. Just as heat waves stress our bodies, they also strain our minds—intensifying existing mental health conditions and creating new psychological burdens. In our changing climate, protecting beings must be as essential as seeking physical shelter from the scorching sun” he adds.
Indeed, evidence shows that exposure to heat can lead to increased suicide rates, acute stress reactions and adjustment disorders, acute and transient psychosis and relapse of bipolar disorders, grief or depression, and schizophrenia. Recurrent disasters like floods and droughts due to temperature rise can lead to post-traumatic stress syndrome, stress, or anxiety among people, mainly adolescents.
Heat waves can lead to rise in vector borne diseases
Hot and humid conditions can also lead to a rise in vector-borne diseases like dengue, chikungunya, Japanese encephalitis, lymphatic filariasis, hemorrhagic fever with renal syndrome, and Zika virus. This is because higher temperatures, rainfall, and humidity create ideal conditions for mosquito breeding and proliferation, leading to these diseases.
Impact on reproductive health
Studies show that that long-term exposure to high temperatures can lead to adverse pregnancy outcomes such as stillbirth, miscarriage, low birth weight, and preterm deliveries. High temperatures can also increase chances of gestational hypertension and preeclampsia.
Uma Aslekar from ACWADAM shares her experiences with women agricultural workers from Shirsao village from Dharashiv. “In spite of adequate rainfall last year, heatwaves have led to drought-like conditions due to increased evaporation, declining water levels in wells, and decreased soil moisture. Water quantity and quality are problems, and women have only a limited amount of water to drink as the water in the region is getting highly saline. In many instances they have to survive on a meagre 1 litre of water for the whole day. This has led to genitourinary problems and a high incidence of kidney stones in the region.”
Malnutrition among children
Increased heat can lead to dehydration and malnutrition among children. Mahapatra, B et al., in their study have found that “High heat can lead to a crisis in food production, which is linked to child malnutrition, with children in districts highly exposed to climate risks being more likely to suffer from stunting, wasting, being underweight, and anaemia compared to those in areas with minimal vulnerability.”
The poor are most vulnerable to the impacts of heat waves
Rekha works as a maid servant in high-rise buildings in Pune and has to walk for almost half an hour every day to two or three houses for work in the scorching sun.
“It is so tiring to walk every day in the sun, but I can’t afford to take a bus or rickshaw every day. I am so exhausted; I have regular cramps, dizziness, and a severe headache. But I can at least use the washrooms when I am at my place of work and get to drink water. My house does not have a water connection, and I have to collect water every day and store it at home. With summer, the supply is even more erratic,” she adds.
Studies from Odisha and Ahmedabad find that heat-related symptoms (HRS) and heat-related illnesses (HRI) such as heat exhaustion, cramps, and heat stroke are common among slum dwellers, those over 60 years old, those with pre-existing medical conditions, those working outdoors, and those with limited water access or information.
Seema Kulkarni from SOPPECOM states, “Apart from severe health impacts due to rising temperatures, women farmers experience a lack of paid employment in agriculture. Dehydration due to walking long distances in search of water has already incapacitated women who now can no longer find work. This has led women scavenging for work for their survival. Climate change has further exacerbated the challenges they face due to systemic inequalities,” she adds.
Heat strain symptoms like excessive sweating, thirst, dizziness, muscle cramps, headache, nausea/vomiting, fainting, or prickly heat/rashes; urogenital symptoms; productivity losses; and renal function loss are common among people from occupations who are exposed to extreme heat, like the salt pan workers and workers of the steel industry.
Impact of heat on animal health
Heat stress negatively impacts dairy animals, resulting in reduced food intake, decreased milk yield, lower milk quality, and poor reproductive performance. The annual milk loss caused by excessive heat in India ranges to around Rs. 2661.62 crores each year.
What is being done at the policy level to deal with heat waves in India
The Climate Hazards and Vulnerability Atlas of India by the IMD keeps a tab on the thirteen most hazardous meteorological events, including heat waves that are known to take a toll on health, cause loss of lives, injury, property damage, and loss of livelihoods and services.
Heat Action Plans (HAPs) have been made to cope with heatwaves
IMD has started Heat Action Plans (HAPs) in many parts of the country in collaboration with the National Disaster Management Authority (NDMA) and local health departments to forewarn about heat waves and also plan action to be taken. The HAPs have currently been implemented in 23 states that are prone to heat waves.
How are the HAPs being implemented at present?
A recent analysis of the implementation of HAPs in nine cities in 9 Indian states by Sustainable Futures Collaborative finds that all cities are prepared in terms of short-term emergency measures like access to drinking water, changing work schedules, and boosting hospital capacity before or during a heat wave.
However, focusing on long-term solutions to reduce the increasing risk of heat waves is inadequate with the only focus being on health systems. Other actions, such as the expansion of urban shade and green cover, the creation of open spaces that dissipate heat, and the deployment of rooftop solar that could help with active cooling, among others, are implemented haphazardly without adequate attention to communities and areas that experience the greatest heat risk.
Many important long-term actions, such as making household or occupational cooling available, developing insurance cover for lost work, expanding fire management services for heat waves, and electricity grid retrofits to improve transmission reliability and distribution safety, are entirely absent in the plans. Other actions, such as the expansion of local weather stations for more granular data on heat variation within a city, mapping urban heat islands, and training heat plan implementers, are only seen in some cities.
The analysis finds that the shift towards long-term climate adaptation will require better planning, coordination, more manpower, developing capacities, and more finance to make them sustainable in the future.
What can you do to prevent the impacts of heat waves?
The IMD recommends:
Avoiding exposure to heat
Preventing dehydration by taking in plenty of water and other fluids such as ORS, homemade drinks like lassi, torani (rice water), lemon water, buttermilk, etc., to maintain hydration levels.
Wearing loose clothing and protecting oneself from the sun by using goggles, caps, umbrellas, etc.
Preventing exposure of the vulnerable to the sun in cases of extreme heat.
Avoiding strenuous activities when the outside temperature is high.
Avoid working outside between 12 noon and 3 PM
Carrying a water bottle along while travelling and avoiding tea, coffee, and carbonated soft drinks, which dehydrate the body, and high-protein food and stale food.
See a doctor immediately if you feel like fainting or experiencing discomfort.
The detailed instructions on the do’s and don’ts and first aid in times of sunburn, heat cramps, heat exhaustion and sunstroke recommended by IMD during heat wave conditions can be found here
The World Health Organisation too recommends prevention of dehydration and of exposure to extreme heat to prevent heat strokes. It suggests:
● Seeking help in case of symptoms such as dizziness, weakness, anxiety, intense thirst, and headache by moving to a cool place as soon as possible and measuring body temperature.
● Resting immediately in a cool place in case of painful muscular spasms (particularly in the legs, arms, or abdomen, in many cases after sustained exercise during very hot weather) and drinking oral rehydration solutions containing electrolytes. Medical attention is needed if heat cramps last more than one hour.
● Call an ambulance immediately in case of unusual symptoms such as hot, dry skin and delirium, convulsions, and/or unconsciousness.
More details can be viewed in the WHO factsheets on Heat and Health