Hotter Nights, Shorter Sleep: Why South India Is Losing More Rest Than the Rest of India
As nights grow warmer across South India, sleep is becoming another casualty of climate change. A new analysis finds that rising nighttime temperatures are cutting into people’s sleep, with potential consequences for health, productivity and quality of life.
Warmer nights driven by climate change are making it harder for many people, particularly in South India, to get a restful night's sleep. Representational image. Image credit: Olena Miroshnichenko/ Pixabay
For many people in South India, the day’s heat no longer ends when the sun goes down. Even late at night, bedrooms, and sometimes even the bed itself, remain warm. Ceiling fans only circulate hot air, windows stay open in the hope of a breeze that never arrives, and falling asleep takes longer than it used to. Over time, these restless nights add up to sleep loss. Scientists now say this is more than a seasonal inconvenience. It is one of the quieter ways climate change is beginning to affect everyday life.
An analysis by Climate Central estimates that people across southern India lose between 78 and 91 hours of sleep each year because nights remain too warm. About eight to nine hours of that loss is directly linked to climate change, making southern India one of the worst-affected regions outside the Middle East.
Unlike heatwaves, which make headlines for a few days, sleep loss is harder to notice. It builds slowly. One restless night becomes another, until weeks of poor sleep begin to affect health.
Why South India is Feeling It First
Puducherry records the highest annual sleep loss in the country at 92 hours per person. Andhra Pradesh follows with 88.6 hours, while Kerala is close behind at 88.3 hours. Tamil Nadu records the biggest climate change impact with 7.9 hours of additional sleep loss every year linked to rising temperatures. Karnataka follows at 7.8 hours.
These figures are not surprising when you consider how summers feel across much of South India. Unlike places where temperatures drop sharply after sunset, many parts of the region remain hot and humid well into the night. Humidity makes it harder for sweat to evaporate, which is how the body cools itself. When that cooling process slows down, getting comfortable enough to sleep becomes much harder.
That is why states that are not always the hottest during the day can still have some of the country’s warmest nights.
Cities are Holding on to the Day’s Heat
Roads, buildings and concrete surfaces soak up heat throughout the day. Instead of cooling quickly after sunset, they release that stored heat for hours, keeping neighbourhoods warmer than nearby rural areas.
Among India’s largest metros, Chennai records the highest overall sleep loss at 93 hours a year. Mumbai and Kolkata follow. Bengaluru, however, tells a different story. Known for its mild weather, the city now records the strongest climate change signal among the metros studied, with 12% of its temperature-related sleep loss linked to climate change. Hyderabad is not far behind.
Sleep Needs a Cooler Body
The body naturally lowers its temperature before entering deep sleep.
When nights stay warm, that process takes longer. People may struggle to fall asleep, wake up several times during the night or wake earlier than usual. Even if they spend enough hours in bed, the quality of sleep suffers.
An illustration representing sleep loss, a growing health concern as hotter nights linked to climate change make it harder for people to get sleep. Representational image. Image credit: Shvetsproduction/Pexels
Climate Central’s analysis shows that nighttime temperatures have risen faster than daytime temperatures in many parts of the world. Across the 1,338 cities studied worldwide, climate change has at least doubled temperature-related sleep loss since the early 1970s.
Why Does One Constantly Feel Tired
Older adults, women and low-income communities are among those most affected by warmer nights. Weaker immunity, heart disease, diabetes, anxiety, depression and reduced concentration have all been linked to this. Staying cool is not an option for everyone
Air conditioning can make a difference, but it remains out of reach for many households. In homes with concrete roofs, poor ventilation or unreliable electricity, indoor temperatures often remain high well after midnight. For families living in these conditions, sleep becomes another inequality shaped by climate.
Heat Plans For Day and Sleep Loss at Night
India’s heat action plans are mostly built around daytime temperatures. They issue warnings about afternoon heat, advise people to stay indoors and encourage hydration.
But the night receives far less attention. Yet it is during those cooler hours that the body is supposed to recover from the day’s heat. As nights become warmer, that recovery is becoming more difficult. Cooler buildings, more trees, better-designed neighbourhoods and affordable access to cooling will all matter if cities are to remain livable.
For millions across South India, climate change is no longer measured only by the afternoon temperature. It is measured by how often they wake up in the middle of the night, waiting for the room to cool down.
EP Staff is the editorial team at EdPublica, an independent media organisation focused on science, education, environment and public policy. The team produces evidence-based news, features, explainers and analysis on issues that shape society and everyday life.
KSBB Workshop Examines Biodiversity, Climate and Environmental Reporting
The Kerala State Biodiversity Board’s three-day media capacity strengthening workshop brought journalists and biodiversity experts together to deepen understanding of Kerala’s rich ecosystems, conservation challenges and the role of informed environmental reporting.
Participants listen to Chairman of KSBB Dr. N. Anil Kumar during the Kerala State Biodiversity Board’s three-day Media Capacity Strengthening Workshop held at SAMETI, Kerala.
From shrinking paddy fields and an eroding coastline to rising human-wildlife conflict and the spread of invasive species, biodiversity loss in Kerala is increasingly showing up in the places and problems that shape everyday life. Yet much of this remains reported as separate environmental issues.
A three-day workshop by the Kerala State Biodiversity Board (KSBB) sought to bring these connections into sharper focus, bringing journalists together with scientists, biodiversity experts, policymakers and community practitioners to explore how climate and biodiversity stories can be reported with greater scientific depth and local context.
The Media Capacity Strengthening Workshop on Biodiversity Conservation and Climate Adaptation, held from September 17 to 19 at the State Agriculture Management and Extension Training Institute (SAMETI), Anayara, Thiruvananthapuram was organised by KSBB in association with the National Biodiversity Authority (NBA). It was aimed primarily at mid-career journalists covering environment, climate, science, development, agriculture, forests, wildlife and communities. Kerala Environment Minister Sunny Joseph attended the inaugural session, along with KSBB leadership, representatives and other invited guests.
Kerala Minister for Electricity and Environment Sunny Joseph inaugurates the Media Capacity Strengthening Workshop organised by the Kerala State Biodiversity Board at SAMETI by lighting the traditional lamp.
The programme focused on six themes: climate resilience and carbon neutrality, agrobiodiversity and food security, marine and coastal ecosystems, urban biodiversity and heat stress, human-wildlife conflict, and invasive alien species. Field engagements were also included to connect scientific and policy discussions with local ecosystems and communities.
Biodiversity as a Climate Story
The workshop examined Kerala’s 98 Ecologically Sensitive Area villages covering 8,711.98 sq km, and the role of forests, wetlands and other ecosystems in reducing climate risks such as floods, landslides and erosion. These ecosystems also function as carbon sinks and support local livelihoods.
Human-wildlife conflict was another major focus. KSBB’s workshop material records 390 human deaths and more than 5,400 injuries from wildlife attacks between 2021 and 2025, with elephants accounting for 111 fatalities. More than ₹41 crore has been disbursed as compensation since 2021.
Agriculture was discussed through the lens of both biodiversity loss and food security. Paddy cultivation in Kerala has declined by more than 75% since the 1970s, from over eight lakh hectares to less than two lakh hectares. The loss of traditional crop varieties and increasing monocropping were discussed as concerns for long-term agricultural and climate resilience.
The marine and coastal sessions examined Kerala’s 600-km coastline, coastal erosion, declining fish catches, blue carbon and community-based fisheries governance. KSBB’s workshop material notes that nearly 45% of Kerala’s beaches have experienced erosion, while fish catch has declined by about 20% over the past decade.
Urban biodiversity was considered through the example of Thiruvananthapuram, where KSBB has developed a City Biodiversity Index based on the Singapore Index framework. The index maps urban trees, wetlands, ecological corridors and biodiversity parks to bring biodiversity considerations into urban planning.
The workshop also examined invasive species including Senna spectabilis, Mikania micrantha, Eichhornia crassipes and Tilapia, and the pressures they place on native biodiversity, agriculture, forests and aquatic ecosystems.
The Role of KSBB
The Kerala State Biodiversity Board is an autonomous body under the State Environment Department, headquartered in Thiruvananthapuram. It functions under the Biological Diversity Act, 2002, the Biological Diversity Rules, 2004 and the Kerala State Biological Diversity Rules, 2008. Its mandate includes conserving and protecting the state’s agro, plant and fish diversity.
The Board’s work includes Biodiversity Management Committees (BMCs), People’s Biodiversity Registers (PBRs), Biodiversity Heritage Sites, research and awareness programmes, and Access and Benefit Sharing (ABS). These mechanisms connect biodiversity documentation and conservation with local governments and communities.
The workshop was also aligned with the Kerala State Biodiversity Strategy and Action Plan (K-SBSAP) 2025–2035, which provides a framework for conserving, restoring and sustainably managing the state’s biological and cultural heritage.
By bringing journalists into conversations with scientists, officials and communities, the three-day programme sought to make biodiversity reporting less confined to technical conservation issues and more attentive to the questions that affect everyday life, from food and livelihoods to heat, floods, wildlife conflict and the resilience of Kerala’s ecosystems.
A woman shields herself from the summer heat on a busy street in India.. Image credit: Anurag Jamwal/Pexels
Climate-driven heat exposed 117 million people in India to a month or more of risky heat between June and August 2026, according to a Climate Central analysis.
Between June and August this year, 117 million people in India spent a month or more under heat that would have been far less likely without a warming planet. That single number, from a new global analysis by Climate Central, puts India at the top of the world’s list for population exposed to climate-driven risky heat — ahead of China’s 94 million and Indonesia’s 83 million.
The finding sits inside a larger, starker pattern. Worldwide, over 1.5 billion people experienced 30 or more days of risky heat that climate change made significantly more likely this summer. On any single day of the season, more than a quarter of humanity felt a strong climate change signal in the local temperature. Climate Central’s scientists tracked this using their Climate Shift Index (CSI), which measures how much more likely a given day’s warmth was because of climate change, and flagged “risky heat days” as those hotter than 90% of what a place recorded between 1991 and 2020 — the threshold at which heat starts to strain the body.
The Global Climate-Driven Heat Scoreboard
Europe came out the most unusually hot continent on the planet this year, even though it was not the most populous one affected. Eighty-nine per cent of Europeans — nearly nine in ten — spent a month or more under risky heat. France and the Holy See tied for the largest temperature anomaly of any country, running 3.5°C above their historical norm, and seven of the world’s ten most abnormally hot countries were European. Fifty-four countries recorded their hottest June-to-August since 1970, France, Italy and the United Kingdom among them.
Asia, by contrast, carried the largest raw number of people through this heat: 2.8 billion, or 58% of the continent’s population, spent 30 days or more under conditions strongly shaped by climate change. India and Egypt were the two countries where more than 100 million people each crossed that threshold.
Africa’s story shows up less in totals and more in persistence. Six African countries spent at least 95% of the entire three-month period under a strong climate change influence — Rwanda for 91 days, Uganda for 89, Ethiopia for 88. For those populations, the season did not have an unusually hot patch; nearly the whole summer was one.
In North America, four in five people in the United States lived through a month’s worth of risky summer heat, with the average American gaining 23 such days from climate change and the average Canadian gaining 17.
India’s numbers, city by city
Nationally, India ran 0.7°C warmer than its 1991–2020 June-to-August average, and the average Indian experienced climate change’s fingerprint on local temperature for 39 days across the three months — better than a third of the entire season.
City-level data obtained alongside the release shows how unevenly that heat landed.
City
State
Days with strong climate signal
Risky heat days
Risky heat days added by climate change
Mumbai
Maharashtra
86
24
4
Pune
Maharashtra
76
17
17
Surat
Gujarat
74
26
9
Bengaluru
Karnataka
73
0
0
Madurai
Tamil Nadu
70
23
23
Nashik
Maharashtra
67
20
19
Coimbatore
Tamil Nadu
66
0
0
Visakhapatnam
Andhra Pradesh
65
21
9
Tiruchirappalli
Tamil Nadu
64
29
29
Chennai
Tamil Nadu
60
40
30
Vijayawada
Andhra Pradesh
43
18
10
Srinagar
Jammu and Kashmir
28
53
29
Source: Climate Central, June–August 2026 city dataset.
Two different stories run through these columns, and conflating them misses the point.
Mumbai tops the country for sheer duration: 86 of the 92 days in the season carried a strong climate change signal, more than any other Indian city measured. But of Mumbai’s 24 risky heat days, only four were added by climate change — the city runs hot most of the year regardless, so the climate contribution to its worst days is comparatively small. Pune and Nashik, sitting in Mumbai’s own state, show almost the opposite ratio: nearly every risky heat day they had this summer would not have happened without climate change.
Chennai had both the most risky heat days in the country — 40 — and the most added by climate change — 30. That combination makes it the city where the analysis draws the clearest straight line between a hot summer and a warming climate. Tiruchirappalli and Madurai, both in Tamil Nadu, follow the same pattern: every risky heat day counted in each city was one climate change made more likely.
Srinagar is the outlier worth pausing on. A city known for temperate summers recorded 53 risky heat days, more than any other Indian city in the dataset, of which 29 were attributed to climate change — a scale of departure from its own historical baseline far larger than what Mumbai or Delhi saw from theirs.
Where the heat did not arrive
Not every Indian city ran hotter than usual. Jaipur’s seasonal average came in 0.4°C below its 1991–2020 norm, Kota 0.2°C below, and Bhopal 0.1°C below — small numbers, but real ones, in a summer when most of the country and the world trended the other way. Even so, none of the three escaped the climate signal entirely: Jaipur still logged three risky heat days attributable to climate change, Kota three, Bhopal one. The exceptions are a reminder that a warming climate does not raise every thermometer in lockstep, even as it raises the odds almost everywhere.
What the numbers are measuring
The CSI framework Climate Central uses does not ask whether a heatwave happened — it asks how much more likely climate change made it. A CSI level of 2 or higher, the threshold used throughout this analysis, means the day’s warmth was at least twice as likely because of the human-driven build-up of greenhouse gases. That is a probability statement about cause, not a one-off weather reading, which is what allows the same framework to compare Mumbai’s long hot stretch against Chennai’s sharper, more clearly climate-driven spike.
Kristina Dahl, Climate Central’s vice president for science, described the pattern as one where “human-driven warming is pushing communities beyond safe physical limits” — a line written with Europe and North America in mind as much as South Asia. The India numbers suggest the same pressure is arriving unevenly within a single country: some cities absorbing a long, low-grade climate signal across most of the summer, others taking a shorter but far sharper hit concentrated into their worst weeks.
August 2026 tied July 2023 as the warmest month ever recorded globally. Record ocean temperatures and strengthening El Niño conditions add another dimension to the climate signal, with implications for India’s already uneven monsoon.
People gather along a waterfront at sunset as the world records increasingly high temperatures. Representational image. Image credit: Samet Çolakoğlu/Pexels
August 2026 tied July 2023 as the warmest month ever recorded globally. But the significance of the latest record lies beyond the temperature figure itself. Heat was building across the oceans, western Europe endured its hottest summer on record, and in India, a strengthening El Niño was adding pressure to an already uneven monsoon.
The global average surface air temperature in August was 16.96°C, 0.85°C above the 1991–2020 average, making it the warmest August in the ERA5 record. Relative to the estimated 1850–1900 pre-industrial average, temperatures were 1.65°C higher. It was the first month to cross 1.5°C since November 2025.
A single month above 1.5°C does not mean the Paris Agreement’s long-term temperature threshold has been breached. That threshold is assessed over a much longer period. What the August figure does show is how far short-term temperatures can now move beyond the historical baseline.
The Oceans Are Sending Their Own Signal
The heat was not confined to the atmosphere. Extra-polar oceans recorded their warmest August in the ERA5 dataset, with an average sea surface temperature of 21.07°C. That was also tied with March 2024 for the highest monthly average recorded for any month.
The tropical Pacific was particularly warm as El Niño conditions strengthened. Around Europe, Atlantic and western Mediterranean waters reached record August temperatures, alongside widespread strong or severe marine heatwaves. The ocean matters here because its warmth can influence atmospheric circulation, rainfall and marine ecosystems. In 2026, its connection to India’s monsoon was particularly relevant.
India Was Watching the Pacific
For India, the global temperature record arrived against a difficult monsoon backdrop. The India Meteorological Department had forecast below-normal rainfall for the 2026 southwest monsoon. By August 2, cumulative rainfall was 12% below the long-period average, with 47% of districts facing deficient or large-deficient rainfall. IMD attributed part of the suppressed monsoon circulation to the development and strengthening of El Niño conditions in the equatorial Pacific.
The deficits were not uniform. By early August, Kerala and Mahe were 22% below normal, while 16 meteorological subdivisions had rainfall deficits ranging from 20% to 38%.
That does not mean August’s global heat record caused India’s rainfall deficit. The monsoon is shaped by several interacting climate systems, and El Niño is only one of them. But the concurrence is significant: while the tropical Pacific was registering exceptional warmth, India was dealing with a monsoon season that was already running below its seasonal benchmark.
Europe Shows the Cost of Persistent Heat
Western Europe had its warmest summer on record in 2026, surpassing the previous record set in 2003. Heatwaves arrived early and persisted through the season. Heat was accompanied by prolonged dryness. Severe drought conditions were reported in France, the UK, Hungary, Romania and Serbia, while exceptionally low river flows affected the Rhine, Danube, Southern Bug and Dnieper.
The connection is important: extreme heat does not operate in isolation. When high temperatures persist alongside rainfall deficits, their effects can accumulate across agriculture, water systems, ecosystems and wildfire risk.
The Record Is Becoming the Background
August’s warmth is more revealing when viewed alongside the other records surrounding it. The month saw exceptional ocean temperatures and low sea-ice levels, while June–August was jointly the warmest global summer on record, matching 2024.
Source: Climate Change Service
The challenge in interpreting such records is to look beyond the headline number. A record month does not mean every region experienced record heat. It means the global climate system is operating from a warmer baseline, while regional weather continues to be shaped by monsoons, El Niño, ocean temperatures and other climate patterns. August 2026 was another record. Its importance may ultimately lie in how quickly records such as this stop looking extraordinary.