How has it been to live in Colombo lately? How often do you think of air conditioners or at least, how often have you been using air conditioning?
Colombo's heat has surged in recent years, turning life in the city to a literal nightmare. Many residents will agree that getting a good night’s sleep has become nearly impossible due to the immense nocturnal heat. In 2024, Colombo recorded its highest average monthly temperatures in history, predicting that it could only be getting worse. While climate change plays a major role in rapid heat waves, the way that the cities are being designed only contributes to the problem. In Colombo, the accelerated urbanization, reduction of urban forest cover and the rise of the concrete jungle has contributed to a lesser known but deeply harmful phenomenon: the Urban Heat Island effect.
Reflecting on Colombo: A transformed city
There is no doubt that Colombo has had one of the most accelerated growth rates in less than a decade. In the late 1990s and early 2000s, Colombo developed at a slower pace and maintained a considerable green cover, creating a favourable climate mixed with the sea breeze. While the rapid post-war development has contributed largely to the economy and the tourism industry of Sri Lanka, it was one of the major contributors to the growing heat of Colombo. The statistics show that Colombo’s Urban cover has increased by 40% during 1997 to 2017 (Wijerathna et al., 2021), suggesting that the numbers are much higher at present. A city that once had colonial style low-rise buildings has now turned into a dense urban hub with a notable skyline.
The Science Behind the Heat
A. Effects of Global Warming
It must be accepted that Global Warming plays a major role in intensifying the other factors that contribute to the urban heat increase. Yet, the topic of Global Warming is not given much prominence in Sri Lanka and even when it is addressed, it is among the few who actually sees the effects of Global Warming. But one might hear complaints from family, friends, or colleagues about sleepless nights due to the persistent heat. Dangerously yet, IPCC’s sixth annual report, 2021, depicts that the night time minimum temperatures are rising faster than the day-time maximums, suggesting a major climate shift. The meteorological department furthermore showcases that extreme heat days of 36-38 oC may now occur frequently in March - May seasons. All these facts and data points to one clear truth: Climate change is here and yes, it is affecting Sri Lanka. The increase of surface temperature of Colombo city by 1.6 oC between 1997 and 2017 due to urban expansion not only confirms the effects of global warming in the city, but also alarms about a much worse tomorrow.
B. The Urban Heat Island (UHI) Effect
Before explaining the intensity of the effect, it is better to understand this lesser-known phenomenon. The Urban Heat Island (UHI) effect refers to the significant increase of the temperature of the urban areas compared to their surrounding rural areas, especially at night. This is due to a combination of human activities, building materials and infrastructure. Urban areas tend to absorb heat by built surfaces. This absorbed heat gets trapped between tall buildings and narrow roads, creating what is known as “urban canyon effect”. More factors such as lack of vegetation and human activities such as vehicles, air conditioners and electricity usage release waste heat, further adding to the trapped heat and warming up the surrounding.
Although one may think of a city like the New York City when reading the above scientific explanation, the effects of UHI are very much present in Colombo city as Colombo has developed a strong UHI where urban areas are 1.5 - 3 oC higher than the surrounding areas (De Silva & Ekanayake, 2016). A spatial analysis done using MODIS thermal satellite data furthermore confirms that “Heat islands are clearly visible in the city core and intensify during dry seasons” (Hearth & Ratnayake, 2016).
Impact on Daily Life
The rising heat of the city does not only irritate the residents but also impacts their lives both directly and indirectly. Heat related illnesses such as heat strokes, dehydration have increased, particularly for children and outdoor workers. In February, 2024, the Ministry of Education suspended all sports activities for 2 days, followed by a detailed guideline due to the extreme heat prevailed during the days. The same guideline can be seen in February, 2025, showcasing how the heat is already affecting the school children, predicting a possible threat to the education and after school sports activities in the near future.
The rising urban temperature leads to more energy consumption as everyone’s life depends on the continuously spinning fans and the air conditioners. This is indeed directly affecting the lives of the civilians as there will be an increase in their electricity bill. Yet, it is a further burden for the electricity suppliers as the depend is high in the Urban areas. As a result, electricity consumption in Sri Lanka peaked during heat waves, largely due to the increased use of fans and air conditioners (PUCSL, 2022)
The low-income communities of Colombo face greater vulnerability due to the rapid increase of heat in the city. Poor ventilation and tin-roofed homes, especially in slum areas and densely populated areas in Dematagoda, Wellawatta, Dehiwala, are direct victims of the unbearable heat waves that Colombo experiences from time to time. It must also be mentioned that outdoor laborers such as construction workers and delivery personnel may experience reduced work hours due to unsafe heat conditions. According to the international labour organization (2021), Sri Lanka risks losing over 1.2% of total working hours by 2030 due to heat stress, impacting the GDP of the country.
Way Forward: Planned Cities & Stronger Policies
A well laid out plan is urgently required to combat the impacts of the temperature rise in Colombo. The Environment Impact Assessment is mandatory in every development activity that takes place within the country. However, it is crucial to introduce an Urban Heat Impact Assessment, prior to approval of the development project via the Colombo municipal council to assess the contribution to Colombo’s heat island. Moreover, updating the Colombo Metropolitan Regional Structure (CMRSP) to include components such as prohibition of heat-intensive materials in dense urban areas and tree-to-concrete minimum ratio for all construction projects are initiatives that should be taken urgently. Communities can also participate in heat-resilient urban restructuring by transforming underused public land such as, rooftops of government buildings, schoolyards, balconies and transit stops, into community green spaces.
The Colombo Municipal Council may also advise the schools in Colombo to expand their schoolyards by integrating shaded learning spaces, trees and naturally cooling play areas, helping children to cope with heat waves. More importantly, the urban planners are encouraged to introduce the vertical garden concepts for all residents as well as the workplaces as it may help drastically in reducing the canyon effect in Colombo city. Although Colombo is already a planned city, integrating climate resilient strategies has proven to be challenging. Yet, even the minor step could make a greater impact.
Urban planning alone may not be sufficient to tackle the issue hence, the support of the country’s legal system is much required. Although many might be unaware, it is crucial to highlight that Colombo City does not have an Urban Climate Resilient Policy. One may argue that such a policy dedicated to a city is unnecessary as the national climate policy exists. In such a context, why must Colombo have its own urban Climate Resilient Policy? Simply because the major threat of rising temperatures in the city due to the urban heat island effect only prevails largely in Colombo so far. Hence, the requirement of such a policy with a dedicated chapter on urban heat mitigation must be introduced under the Urban Development Authority or the Colombo Municipal Council for making better decisions and mitigation strategies. Furthermore, the Colombo Municipal Council should be encouraged to introduce cooling ordinances such as green walls, cool roofs and covered walkways in order to optimize the maximum heat resilience in development projects.
Conclusion: Rethinking Colombo for a Better Future
The sleepless nights, exhausting afternoons and the immense heat indicate that the effects of climate change are here and Colombo, unfortunately is becoming a prime victim of it at an alarming rate. Government bodies, the general public and other environmental organizations must urge the need of a strategic system to combat the heat crisis that is immense in Colombo. This article does not intend to deny the impacts of global warming that affects the whole of Sri Lanka but rather highlight the immense heat waves that Colombo keeps experiencing, which is unusually high compared to the other regions. This may be the problem of Colombo today but will soon be an island wide issue covering all major cities. Hence, now is the time for awareness, action and implementation of a well laid out framework to combat and avoid urban heat islands through better urban planning, restructuring and updated policies before it is too late.
References:
Department of Meteorology Sri Lanka. (n.d.). Weather and climate data.
De Silva, R. P., & Ekanayake, E. M. S. (2016). Urban heat island effect: Case study in Colombo metropolitan area. Sri Lankan Journal of Geology and Earth Sciences.
Herath, S., & Ratnayake, H. (2020). Land surface temperature trends in Colombo using MODIS satellite data. Remote Sensing.
Public Utilities Commission of Sri Lanka. (2022). Annual report 2022.
UNDP Sri Lanka. (2020). Climate risk country profile: Sri Lanka.
Wijerathna, C. D., Herath, H. M. W. A., & Gunathilake, S. K. (2021). Monitoring urban heat islands in Colombo using remote sensing data from 1997 to 2017. Remote Sensing of Environment.
World Bank Group. (2022). Climate change knowledge portal: Sri Lanka.
