Satellite Images Show How Cities Are Heating Up

We looked at studies that analysed data from nine cities spanning up to five decades. The images reveal three patterns: extreme sprawl that replaced natural landscapes with concrete, the paradox of the city that added trees but still got hotter, and the systematic loss of water bodies that once cooled urban environments.

As cities turn into heat islands, India’s urban population exposed to high temperatures is estimated to rise eightfold by 2050, as IndiaSpend reported in the first part of this series. Vulnerable communities, unable to afford cooling, will suffer the most.

“This inevitable development could exacerbate the Urban Heat Island crisis our cities are already facing and further reduce the quality of living," says Abhiyant Tiwari, climate resilience lead and health consultant at the Natural Resources Defense Council.

Every city shows increased built-up area and rising land surface temperatures. But the details vary. Bengaluru experienced the most extreme sprawl and temperature rise. Hyderabad presents a paradox—green cover increased 197%, yet LST rose 7.55°C. These variations reflect different urbanisation drivers: Bengaluru's tech boom, Hyderabad's IT and pharmaceuticals, Patna's administrative role, Chennai's haphazard expansion.

Extreme sprawl

In Bengaluru, built-up area rose ten-fold from about 6,000 hectare in 1973 to 64,000 hectare in 2023, accompanied by a fall in area of vegetation cover (88%) and water bodies (79%) from 69,000 hectare to 9,900 hectare, researchers at the Indian Institute of Science have found.

Just in the last three decades, this urban sprawl has caused the overall average LST in Bengaluru to rise by 15.13°C, according to a study by researchers at the city’s Christ University and Qatar University.

From a climate and public health standpoint, this increase would be classified as “severe and hazardous”, says Shikha Patel, lead author and research assistant at the Department of Architecture and Urban Planning in Qatar University. This rate of increase is not acceptable, she adds, and indicates an urgent need for cooling strategies.

Patel points to the rapid population growth, economic development, and the city's emergence as a major IT and industrial centre as primary factors. The most intense phase of urban sprawl and land use change, as evidenced by satellite images, occurred after the early 2000s leading to the creation of urban heat islands, she adds.

Land use maps of Bengaluru metropolitan area
Source: Urban Transitions, September 2025

In the case of Vijayawada, which saw a 15.84°C rise in LST between 2001 and 2023, the built-up area grew 58%, while the extent of water bodies fell 38% and vegetation declined 42%.

“Vijayawada follows a fan-shaped, unidirectional growth trajectory. Bounded by hills to the east and west and the Krishna river to the south, the city’s expansion has been predominantly oriented towards the northeast,” explains V. Vinoj, associate professor at the School of Earth, Ocean and Climate Sciences, IIT Bhubaneswar. Its location as a transportation hub, and recently, the proximity to the new state capital Amaravati contributed to rapid urban growth. “The older core city region situated near the river exhibits the highest land surface temperatures (LST), highlighting the urban heat concentration in this area,” he adds.

Land Use and Land Cover Change in Vijayawada (a) 2001-2011 (b) 2011-2021 (c) 2021–2023
Source: Urban Transitions, September 2025

In Patna, which saw a 4.5°C rise in LST, the built-up area doubled between 1988 and 2022—most of it after 2005. During this period, the extent of water bodies reduced by 34% and vegetation by 84%.

The city demonstrates a concentric growth model, marked by the city’s radial outward expansion, Vinoj says. Patna functions as the administrative hub while also serving as a major hub for healthcare and education. This role, coupled with significant rural-to-urban migration, continues to shape the city’s urbanisation dynamics, he explains.

Land use change in Patna
Source: Journal of Landscape Ecology, March 2025

Green cover paradox

In Hyderabad, the urban heat island phenomenon is stronger at night. The city is 0.7°C cooler than its peripheries and peri urban areas during the day and 1.9°C warmer at night, according to a 2024 review by the Centre for Science and Environment.

In two decades to 2023, its built-up area doubled, but green cover also rose from 9% to 27%. This in turn has moderated daytime temperatures, the review says, but widespread concretisation still reduces thermal comfort at night. Experts say that the IT boom and the bio-pharmaceuticals industry in Hyderabad have been the main reasons for the increase in population.

"Green cover definitely has increased in Hyderabad due to consistent efforts through the Haritha Haram programme. But this does not offset the UHI crisis or significantly reduce temperatures," says D. Sabarinath, a geographer and urban researcher. "This is largely because forest cover is lost due to rapid urbanisation and this can't be replaced by scattered planting without planning. For example, they grow eucalyptus trees because they mature fast but the capability of evapotranspiration for this species is low. So data shows tree cover has increased but on ground, unscientific tree planting can reduce aquifer levels and cause more damage," he adds.

Growth in urban built-up in Hyderabad
Source: Centre for Science and Environment, Urban Heat Stress Tracker

When planning failed

Mumbai saw its urban sprawl double in about three decades to 2018, a 2021 study in the Journal of the Indian Society of Remote Sensing shows. At the same time, its green cover nearly halved and LST in some areas rose by 1.98°C. Further, a 2024 study in the International Journal of Environmental Science and Technology shows that water bodies too declined by 24% between 1993 and 2023.

“Humidity and wind direction are already factors to consider when it comes to how heat is felt in coastal cities. When urbanisation also gets factored in, the impact of heat gets worse,” explains Lubaina Rangawala, director of urban development and resilience at WRI India.

“This is clear in the way that the Mumbai airport and huge settlements on the eastern and western side experience heat,” Rangawala adds. “Given the sharp dip in the city's vegetation cover, dense low income settlements like Dharavi are 6-8 degrees warmer than the Five Gardens area in Matunga which is just 2 km away."

Land use change in Mumbai
Source: Journal of the Indian Society of Remote Sensing

In comparison, Chennai’s LST rose 6.53°C in the last decade when its green cover reduced by 13%, according to a 2024 study in the Indian Journal of Science and Technology. Between 1985 and 2015, the city’s built-up area rose from 48% to 74%, a 2025 report by the Tamil Nadu Planning Commission shows.

“Except for a few areas like Annanagar and some parts of Adyar, urbanisation in Chennai is largely haphazard,” says M.G. Devasahayam, former civil servant officer who was part of the planning for the city's second master plan. “The city's first masterplan (formulated in 1976) was virtually a real estate plan and the second plan focussed on additional infrastructure. People, thermal comfort and sustainability were not central to this plan. Water bodies that can reduce LST were all encroached upon and built over from the 1990s during the population explosion after Liberalisation and we are facing the heat for this now."

The city’s development is characterised by both north–south expansion along the coast and a half star-like radial spread. Sea breeze moderates some heat in coastal areas, but can't offset the loss of water bodies that once cooled the entire city.

Urban growth in Chennai
Source: Tamil Nadu Planning Commission

In the national capital, LST rose by 5.23°C between 2001 and 2021, accompanied by a 50% increase in built up area. Peak temperatures in this period rose up to 51.60 °C.

Land use change in Delhi
Source: Environmental Technology & Innovation

“When you compare the urbanisation and heat maps of Delhi you notice that hotspots and higher land temperatures are more prominent in the outskirts. This is because Delhi’s core was largely well-planned and has green cover,” says Aravind Unni, an urban practitioner and researcher.

“Importantly, there was a failure in implementation of Master Plan 2001. The Delhi Development Authority and government agencies were to acquire agricultural land and develop it before releasing it for commercial projects. However due to multiple reasons including low compensation rates, the acquisition was stalled and the DDA acquired far less land than planned, creating a shortage of legally developable land. As a result, there was a huge boom of unauthorised colonies and parallel development by private players leading to dense and unsustainable urban sprawl,” he adds.

Smaller cities, similar patterns

Pune’s built-up area increased 43% in three decades to 2019, according to a 2024 study in the International Journal of Geoinformatics. While vegetation initially increased from 36% of its area to 44% in 2010, it subsequently declined to 42% in 2022. LST increased by 4.79°C between 2000 and 2022.

“Pune’s urbanisation has evolved along a polycentric model, characterised by multiple specialised clusters dispersed across the metropolitan region. The presence of numerous IT and automotive industries, along with a concentration of educational institutions, has been a key driver of this growth pattern,” says Soumya Satyakanta Sethi, research scholar in the School of Earth, Ocean and Climate Sciences at IIT Bhubaneswar. “Multiple heatspots can be seen across the city, which was earlier mostly over the central core city region,” he adds.

Peri-urban areas still have patches of agricultural land and natural vegetation, which help mitigate the urban heat island effect to some extent. However, ongoing urban sprawl threatens these remaining green spaces.

Land use changes in Pune (a) 2000, (b) 2010 and (c) 2022
Source: International Journal of Geoinformatics

Similarly, Madurai saw a 5°C increase in LST between 2013 and 2023. Population growth contributed to increased construction activity, vehicle emissions and industrial activities.

Land surface temperature in Madurai, 2013 and 2023
Source: Theoretical and Applied Climatology

Three decades of satellite imagery document a transformation that urban planners can no longer ignore: India's cities have systematically replaced cooling natural systems with heat-trapping concrete.

The patterns are consistent across tier-1 and tier-2 cities alike: extreme sprawl replaces forests and farmland; scattered tree-planting can't offset forest loss; water bodies once concretised are gone permanently.

“Retrofitting cities is harder than creating new plans for cities,” says Vinoj of IIT Bhubaneswar. India's tier-1 cities may have already exceeded their thermal capacity to reverse heat intensification. Tier-2 cities still have a choice—but only if they act on what the satellite data has made impossible to deny.

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