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It's April 2026 and India is sizzling under intense heat this year. The India Meteorological Department has warned that many parts of the country will experience intense heatwaves between April and June 2026. Temperatures in several regions are already touching 42–45 degrees celsius. The India Meteorological Department has warned that heatwave conditions are likely to persist over the next few days, with maximum temperatures expected to climb up to 43°C in several regions.
India is fast turning into the heat capital of the world with nineteen of the world’s twenty hottest cities being located in India, according to the Air Quality Index data released on April 21 at 12:21 pm IST.
These include seven cities from Bihar, two from Odisha, eight from West Bengal and two from Uttar Pradesh. Bhagalpur in Bihar, Talcher in Odisha and Asansol in West Bengal top the list, with temperatures hovering around 44 degrees celsius, the highest anywhere on Earth at the time the data was recorded according to an India Today report. Close behind are other cities such as Begusarai, Motihari, Munger, Bhojpur, and Siwan, along with parts of eastern Uttar Pradesh and West Bengal with temperatures reaching 43 degree celsius.
While northern, central and eastern regions are battling extreme heat, parts of southern and north-eastern India are witnessing a sharp contrast in weather conditions with moisture inflows and thunderstorm activity. These contrasting weather patterns are a clear indicator of rising climate variability, say experts, who warn that these will lead to an increase in both the intensity and frequency of heatwaves in the future.
Scientists warn that humidity could make the heat even more dangerous. As they explain, in high heat the body uses sweating as a mechanism to cool itself. But the air is already filled with moisture under humid conditions, and the body does not produce sweat under these conditions and thus is unable to cool down and allow the heat to dissipate. This consistent rise in body heat can lead to increased heart rate, high blood pressure and organ failure in extreme cases.
A recent CEEW study has found that relative humidity that can aid the severity of the impacts of high heat, has increased by up to 10 percent across North India and Indo-Gangetic Plains over the last decade, where farm workers spend long hours outdoors. Even drier cities like Delhi, Chandigarh, Kanpur, Jaipur and Varanasi are now seeing higher humidity levels.
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.
The heat index is a combination of air temperature and relative humidity and measures how hot it really feels when relative humidity is factored in with the actual air temperature. This is also sometimes referred as Apparent temperature and can be understood as the temperature perceived by the body.
Heat and humidity in India are measured by the India Meteorological Department (IMD) using a network of surface observatories that use thermometers for temperature and hygrometers or psychrometers for humidity measurements. The equipment used to measure heat and humidity include wet/dry bulb thermometers, sling psychrometers, and digital sensors that calculate the Heat Index.
Scientists use wet-bulb temperature (WBT) to understand the combined effect of heat and humidity on the human body. While earlier research found that humans can survive up to a WBT of 35°C, a recent study has concluded that the body begins to lose its ability to control internal temperature at a WBT of around 31°C in hot and humid conditions, which is much lower than earlier estimates. Humid heat can be more dangerous than dry heat as it is less noticeable.
The India Meteorological Department (IMD) issues impact based heat wave 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.
This sharp rise in temperatures is due to a range of factors working together. India is experiencing strong solar radiations during April. Clear skies are aiding direct sunlight to heat the land surface, reduced snow cover in Eurasia and the Himalayas that help in reflecting heat are aiding rise in temperatures. In addition to this, warming of the Pacific ocean, neutral ENSO conditions and dry northwesterly winds, are preventing cloud formation and rainfall leading to high heat conditions.
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.
Current research shows that heat waves will increase pressure on India's electricity and water systems, thus straining the country's infrastructure. This could lead to a significant increase in the gap between water availability and demand under warming scenarios and could 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. The recent surge in heat is leading to a rise in tropical and lifestyle diseases such as dengue and cardiovascular diseases in India.
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 temperatures 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.
It can lead to 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.”
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 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.”
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.
Studies show that for workers in the urban informal sector in India, heatwaves don’t just bring discomfort—they pose serious health and livelihood risks.
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.
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.
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, the focus on long-term solutions to reduce the increasing risk of heat waves continues to be inadequate except in case of health systems to some extent.
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.
In a recent CEEW report, the authors recommend that going beyond daytime temperatures to include night time temperatures when planning for heat risk reduction, notification of heat waves as a state specific disaster, promoting heat insurance to protect livelihoods, creating a national repository of HAPs, tapping into state disaster mitigation funds would be the way forward to deal with rising heat waves in the future.
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