Hyderabad: Warangal’s urban heat index doubled between 2003 and 2023, with heat hotspots expanding alongside industrial growth. But the study does not mean the city is simply ‘as hot as Hyderabad.’
Hyderabad has spent the past few years confronting a familiar problem: as the city expands, concrete, roads and buildings are changing how heat is absorbed and retained. Now, a new study suggests that a similar pattern is emerging in Warangal.
Warangal’s Urban Heat Index
A study published in Scientific Reports has found that Warangal’s Urban Heat Index (UHI) increased from 1.2 in 2003 to 2.4 in 2023, a twofold increase in 20 years. The area identified as a statistically significant heat hotspot also expanded by about 62 per cent during the period.
The findings raise a larger question for Telangana: as cities beyond Hyderabad urbanise and industrialise, are they also creating their own pockets of dangerous urban heat?
What does ‘urban heat index’ mean?
The term can be confusing.
The Urban Heat Index used in this study is not the same as the air temperature reported by a weather station. It is a measure derived from land-surface temperature that looks at the difference in heat between an urban area and its surroundings.
It is a higher value indicates a stronger urban heat island effect, where built-up areas become warmer than their less urbanised surroundings.
The researchers analysed satellite observations, land-use information and meteorological variables from 2003 to 2023 to examine how heat patterns changed across Telangana. They also specifically examined industrial areas and selected Warangal as a case study of a secondary industrial city.
What happened in Warangal?
The study found that Warangal’s mean UHI index rose from 1.2 to 2.4 over the two decades.
At the same time, the expansion of an industrial corridor towards the north-eastern part of Warangal coincided with the spread of high-heat zones. The statistically significant hotspot area increased by around 62 per cent.
This does not mean that industrialisation alone caused Warangal’s rising heat. The researchers point to several interacting factors, including industrial land use, built-up density and near-surface air temperature. Vegetation, meanwhile, acts as a moderating factor.
Same pattern at a larger scale
Warangal is part of a broader change across the state.
The study found that the mean UHI index in Telangana’s industrial areas increased from about 1.35 in 2003 to 2.70 in 2023. Non-industrial areas also became warmer, but the increase was smaller, from 1.00 to 1.82.
Industrial regions accounted for nearly 70 per cent of the expansion of thermal hotspots identified in the study. The researchers found that the share of industrial hotspots increased from 38.2 per cent in 2003 to 53.3 per cent in 2023.
That matters because industrial areas tend to contain large amounts of concrete, asphalt and other impervious surfaces, with less vegetation. Such surfaces absorb and retain solar energy differently from soil and vegetated land.
So, is Warangal becoming another Hyderabad?
There is a parallel, but the two studies cannot be directly compared to declare Warangal ‘as hot as Hyderabad.’
Hyderabad’s heat has also been closely linked to rapid changes in its built environment.
The Centre for Science and Environment’s 2024 Urban Heat Stress Tracker found that Hyderabad’s built-up area more than doubled between 2003 and 2023 from 298.3 sq km, or 20.6 per cent of the city’s geographical area, to 636.58 sq km, or 44 per cent.
The CSE study also found an important day-night difference. During summer daytime, Hyderabad’s urban core could be cooler than surrounding peri-urban areas, while at night the core was warmer, suggesting that built-up areas retain heat after sunset.
The Warangal study, however, uses a different methodology and indicator.
So, it is better to say that both cities show signs of urbanisation changing their heat environment, rather than saying Warangal has reached Hyderabad’s level of heat.
Why should this matter to people living in Warangal?
Urban heat is not just a number on a satellite map.
Hotter built-up surroundings can increase exposure to heat, particularly for people who spend long hours outdoors, including construction workers, street vendors, traffic personnel and other outdoor workers.
Telangana has already recognised the additional vulnerability of urban populations to heatwaves. The state has classified heatwaves as a state-specific disaster, with authorities noting the vulnerability of workers in cities including Hyderabad and Warangal.
The new study therefore offers an early warning about where future heat-management efforts may need to be concentrated.
