India is facing longer, severe heatwaves, putting women, informal workers, and marginalised communities at increased risk. We look into the impact on health and the level of preparedness.

In June, scorching heatwaves gripped large parts of north and central India for at least six consecutive days, with maximum temperatures exceeding 45 degrees Celsius in many cities. The heat index, which measures how hot it feels after taking humidity into account, increased to a worrying 53.8°C in Delhi. However, as temperatures continue to break records, research shows heatwaves will only get worse.

Heatwaves are a “period of unusually high temperatures as compared to what is normally expected over a region,” according to the India Meteorological Department. In India, it is considered a heatwave if the maximum temperature of a station reaches at least 40°C or more for plains and at least 30°C or more for hilly regions. If the temperature increases more than 6.4°C above normal, it is considered a severe heatwave.

This year, India has experienced the third consecutive summer of extreme heat. Now, a recent study highlights that about 57% of Indian districts, which account for 76% of the country’s population, are at high to very high risk from extreme heat. According to the study How Extreme Heat is Impacting India by the Council on Energy, Environment and Water (CEEW), Delhi, Maharashtra, Goa, and Kerala are among the top ten states facing the highest heat risk.

Impact on health

In India, extreme heat has been linked to increased hospital admissions for cardiorespiratory conditions, mental health issues, and reduced productivity. In Surat, mortality rose by 20% on days when maximum temperatures hit 40°C or higher, with a noticeable uptick in hospital visits during hotter periods.

In Odisha, a community-level assessment pointed to heat exhaustion, cramps, and heat stroke as the most common heat-related ailments. Rising temperatures have also contributed to a spike in foodborne and waterborne infections, as well as malnutrition.

High temperatures can further exacerbate cardiopulmonary diseases, especially due to increased exposure to allergens and air pollutants. A 2024 report by the non-profit HeatWatch, documented 733 deaths and over 40,000 heatstroke cases across 17 states between March and June.

Adding to these concerns, research by the CEEW highlights a troubling trend: while the number of extremely hot days is rising, very warm nights are increasing at an even faster rate. These nights—defined as periods when both minimum and maximum temperatures rise above the 95th percentile—are becoming more frequent across the country.

Over the past decade, about 70% of districts experienced at least five additional very warm nights per summer. Cities such as Mumbai recorded 15 extra nights, Bengaluru 11, and Bhopal and Jaipur seven each. These warmer nights prevent the body from cooling down after prolonged exposure to daytime heat, significantly heightening the risk of heatstroke and worsening chronic conditions like diabetes and hypertension. This is especially dangerous for vulnerable and marginalised populations.

According to the World Health Organisation, heat-related mortality among people over the age of 65 rose by nearly 85% between the early 2000s and the 2017–2021 period. In India, men and women aged 45 to 59 have recorded the highest rates of heat-related deaths. States such as Uttar Pradesh, West Bengal, and Andhra Pradesh have reported the most fatalities due to heatstroke.

“When you’re exposed to heat, there is an increase in core body temperature, the internal temperature rises. If it goes beyond one degree from the baseline, for a layman, it’s considered a state of fever,” explains Dr. Vidhya Venugopal, climate scientist. She is also the Professor and Country Director for NIHR GHRC NCD-EC at the Sri Ramachandra Institute of Higher Education and Research in Chennai.

“We consider 98.4 degrees Fahrenheit as normal. But if it reaches 99.4, it’s classified as a fever. You may not feel it externally, but the internal temperature climbs, and once that goes beyond one degree, it’s harmful for the body. We call it heat strain,” she says.

This physiological response, she adds, stems from heat strain. “If it continues to rise, it can lead to heat exhaustion and, eventually, a continuum of heat-related illnesses.”

Image credit: Construction workers in India are particularly vulnerable to the health risks of heat because of factors such as the lack of legal protection and economic disadvantage. Photo by PxHere.

Socio-economic vulnerabilities

With increasing heatwaves and their impact, conversations about rising heat have begun, but their unequal impact remains on the periphery of these discussions.

Women and men experience climate change as well as heat differently. Persisting gender inequities add to their vulnerability, affecting their access to adaptation strategies and solutions. “Women bear the brunt of climate change,” says Dr. Venugopal. “There is a constant imposition of caregiving that they have to adhere to while often being the last to care for themselves,” she says.

She further highlights that women living in the rural areas of states struggling with water scarcity, such as Rajasthan and Bihar, spend a substantial amount of time getting water for their families.

“Moreover, women working in the informal sector in urban and rural areas have to deal with co-risks that impact them more. For instance, many don’t have access to toilets during most of their day, so they limit water and food intake. This leads to more dehydration on high-temperature days,” Venugopal explains.

Several studies have also shown the high impact of heat on informal workers. A Greenpeace India report last year found that about 49% of street vendor respondents in Delhi experienced a loss of income during heatwaves, with 80.08% of them acknowledging a decline in customer numbers.

It also highlighted the disproportionate impact on women vendors. In the study, 7 out of 8 women street vendor respondents reported high blood pressure, and many middle-aged women reported disruptions in their menstrual cycle due to the heat.

In the report, a vegetable vendor, Sabila in Delhi, talked about how she tries to deal with the rising heat. “There is no tarpaulin on the cart, so the hot sun falls directly on my head, making my forehead hot. To cope, I wet my dupatta and put it on my head. It feels fine for a while, but once the dupatta dries, it starts getting hotter again. This leads to headaches due to the heat,” she said.

As a diabetic patient, she needs to sit due to weakness from the sun. “When I do not get a place to rest, the veins in my legs get blocked while pulling the cart. There is a pricking sensation in my knees, and pain starts,” she shared.

Image credit: Construction workers in India are also particularly vulnerable to health risks of heat. Photo by Pxhere.

Construction workers in India are also particularly vulnerable to health risks of heat. They have “few legal protections, a poor safety net, increased exposures to some environmental factors, and are economically disadvantaged,” a 2015 study notes. 

In the conversations about heat and solutions, caste is often excluded, even though research has shown that people from lower castes, Scheduled Castes (SC), Scheduled Tribes (ST), and Other Backward Classes (OBC), experience more heat stress.

A 2024 study found that people from the general caste spent on average 28% of their working hours outdoors, while ST workers spent 43 to 49% outdoors. Moreover, between 2019 and 2022, in at least 65 districts in India, about 75% of SC and ST workers spent 75% of their working hours outdoors.

As people from marginalised castes spend more time working outside, they are more at risk from heat and heat-related illnesses such as stroke, and even death.

Tackling heat

By the end of the century, the frequency of heatwaves is projected to increase by 30 times the current frequency in India, with their duration increasing by 92 to 200 times.

Despite the alarming data, earlier this year, a first-of-its-kind study by Sustainable Futures Collaborative, a New Delhi-based research organisation, found that while all cities reported implementing short-term response measures such as access to drinking water and change in working schedule to prevent the loss of lives during heatwaves, there was a significant gap in their long-term preparedness for future heat.

One of the study’s recommendations is the use of Heat Action Plans (HAPs) to institutionalise long-term actions.

HAPs are “guidance documents prepared by state, district, and city governments to help prepare for, respond to, and recover and learn from heatwaves,” according to the Centre for Policy Research (CPR). The first HAP in India was developed in Ahmedabad in 2013.

In a study, CPR recommends the mandatory inclusion of vulnerability assessments and the identification of urban heat islands in HAPs. It also underscores the importance of allocating national or state public finance towards long-term risk mitigation efforts.

After analysing 37 HAPs at the city, district, and state levels across 18 states, the study found that most HAPs are not built for the local context and have an oversimplified view of extreme heat. Almost all of the HAPs performed poorly in identifying and targeting vulnerable groups. They are also underfunded and lack transparency.

Currently, as HAPs are one of the major strategies to tackle the heat hazard, strengthening them is a crucial need.

“HAPs have been loosely linked to the Ministry of Labour and Employment. All departments many times work in silos. However, if the Ministry of Road, Transport and Highways, the Ministry of Environment, Forest and Climate Change and the Ministry of Health and Family Welfare work together during heat emergencies it will reduce mortality and heat morbidities,” Venugopal explains.

She also notes that heat is not yet considered an emergency and questions the preparedness at the national, state, city, and grassroots levels if adverse events happen.

Moreover, medical professionals are not trained to recognise and treat heat-related illnesses, Venugopal says. “If there is a slight increase in temperature, then they are given paracetamol and sent home. In many cases, heat is not even considered a cause. Sometimes heat strokes are also considered as a cardiovascular event,” she says.

Venugopal underscores the importance of recognising the signs and symptoms of heat-related health issues, especially in the initial stages, so that it is treated before it leads to a heat stroke.

While most studies today emphasise the urgent need to address rising heat and implement solutions, there remains a critical gap: the absence of a comprehensive heat action strategy that accounts for gender and caste inequities. Venugopal also stresses the importance of communicating the impacts of heat in ways that are accessible and relevant to diverse communities and regions.

“Understanding the impact of heat through the lens of health, both physical and mental, livelihoods, social inequities, and environment is crucial,” she concludes.