How Do Urban Heat Islands Form in Mega Cities Like Lagos and Delhi?

Urban heat islands are making megacities like Lagos and Delhi significantly hotter. Learn how urban design, land use, and human activity drive heat buildup and why it matters for climate resilience and public health. 

Written By Warrence Oghenevwegba

Published on January 3, 2026, 9:17 P.M

Cities like Lagos and Delhi are getting hotter at a rate that cannot be explained by global climate change alone. Measured temperature differences between dense urban centers and their surrounding rural areas show a consistent pattern of localized warming driven by how cities are built and operated. This phenomenon, known as the urban heat island effect, has become a defining environmental challenge for megacities experiencing rapid growth.

Why do Lagos and Delhi trap and retain heat so efficiently, and what specific urban processes are responsible for turning these cities into persistent heat zones?

Understanding the Urban Heat Island Effect

The urban heat island effect occurs when urban areas record higher air and surface temperatures than nearby rural locations. This temperature difference can range from 1 to over 7 degrees Celsius, and during extreme heat events it can be even higher. The effect is most noticeable at night, when cities cool down more slowly due to stored heat in buildings and infrastructure.

Urban heat islands form because natural land cover is replaced with materials and systems that absorb, store, and re emit heat. In megacities like Lagos and Delhi, this transformation happens at scale and speed, magnifying the intensity of local warming.

Land Cover Change and Heat Absorption

One of the primary drivers of urban heat islands is the replacement of natural landscapes with artificial surfaces. Vegetation, soil, and water bodies are gradually replaced by asphalt roads, concrete buildings, rooftops, and paved open spaces.

These materials have low reflectivity and high thermal mass. They absorb large amounts of solar radiation during the day and release it slowly after sunset. Unlike vegetation, they do not provide cooling through evapotranspiration. As a result, urban surfaces remain warm well into the night.

In Lagos, rapid urban expansion has significantly reduced green spaces, wetlands, and coastal vegetation. Large areas that once moderated temperature now contribute to surface heating. In Delhi, the expansion of residential colonies, commercial districts, and transport infrastructure has produced a similar outcome, with satellite data showing consistently higher land surface temperatures in dense urban zones.

Loss of Vegetation and Natural Cooling

Vegetation plays a critical role in regulating local climate. Trees provide shade, reduce surface temperatures, and cool the air through transpiration. Grasslands and soils also absorb less heat than built surfaces and allow for better moisture retention.

Both Lagos and Delhi have experienced sustained losses in tree cover and open green spaces due to population growth and development pressure. In many neighborhoods, green areas are fragmented or absent, limiting their cooling impact. Informal settlements, which often lack planned green infrastructure, are particularly vulnerable to elevated temperatures.

The reduction of vegetation not only increases surface heat but also worsens thermal comfort for residents, especially in low income communities where access to cooling technologies is limited.

Urban Density and City Design

The physical structure of cities strongly influences how heat is trapped and dispersed. Dense building arrangements, narrow streets, and high rise developments create what is known as the urban canyon effect. These configurations reduce airflow, limit wind driven cooling, and cause heat to reflect multiple times between surfaces.

Delhi’s dense residential and commercial zones exemplify this pattern. Closely packed buildings restrict ventilation and increase nighttime heat retention. In Lagos, high density developments combined with limited urban planning in some districts contribute to similar heat trapping effects.

Poor ventilation at the city scale prevents warm air from dissipating efficiently, reinforcing the urban heat island effect.

Waste Heat from Human Activities

Beyond surface materials and city design, human activities directly add heat to the urban environment. Vehicles, industrial processes, generators, air conditioning units, and power plants all release waste heat as a byproduct of energy use.

In Lagos, widespread reliance on generators due to power supply challenges contributes significantly to localized heating. Traffic congestion also adds to thermal buildup. In Delhi, high vehicle density, industrial activity, and heavy use of air conditioning during hot seasons intensify anthropogenic heat emissions.

This waste heat does not disperse easily in dense urban areas, further elevating ambient temperatures.

Interaction with Climate Change

Urban heat islands do not exist in isolation from global climate change. Instead, they amplify its effects. Rising baseline temperatures increase the intensity and frequency of heatwaves, while urban heat islands push local temperatures even higher.

In megacities like Lagos and Delhi, this interaction creates compound heat risks. Heatwaves become more dangerous, nighttime cooling is reduced, and heat stress increases across entire populations. Vulnerable groups such as outdoor workers, elderly individuals, and children face heightened health risks.

Environmental and Social Impacts

The consequences of urban heat islands extend beyond discomfort. Elevated temperatures increase electricity demand for cooling, placing stress on energy systems and increasing greenhouse gas emissions. Higher temperatures also worsen air pollution by accelerating chemical reactions that form ground level ozone.

Urban heat islands affect water systems as well. Heated surfaces raise stormwater temperatures, which can harm aquatic ecosystems when runoff enters rivers and lagoons.

Socially, heat exposure is unevenly distributed. Low income neighborhoods often experience higher temperatures due to limited vegetation, poor housing materials, and lack of access to cooling. This creates environmental inequality within cities.

Evidence from Lagos and Delhi

Remote sensing studies using satellite thermal imagery consistently show higher land surface temperatures in urban cores compared to surrounding rural areas in both Lagos and Delhi. These studies link temperature increases to land cover change, building density, and infrastructure expansion.

In Delhi, research has documented temperature differences exceeding 10 degrees Celsius between urban and rural zones during peak summer periods. In Lagos, similar patterns have been observed, particularly in highly built up districts and industrial corridors.

These findings confirm that urban heat islands are not theoretical constructs but measurable, spatially identifiable phenomena.

Strategies for Reducing Urban Heat

Mitigating urban heat islands requires integrated urban planning and environmental management. Effective strategies include expanding urban green spaces, protecting existing vegetation, and incorporating trees into streetscapes and residential developments.

Cool roofs and reflective pavements can reduce heat absorption by increasing surface reflectivity. Improved building design that promotes natural ventilation can also reduce heat accumulation.

At the policy level, heat mitigation must be integrated into land use planning, housing development, transport systems, and energy strategies. Addressing urban heat is not optional. It is central to public health, climate adaptation, and sustainable urban development.

Conclusion

Urban heat islands in megacities like Lagos and Delhi are the product of deliberate choices about land use, infrastructure, energy, and growth. They are shaped by how cities expand, what materials they use, and whose needs are prioritized in urban planning.

As urban populations continue to rise, the cost of ignoring urban heat will increase in the form of health risks, energy stress, and environmental degradation. The challenge ahead is clear. Will cities continue to amplify heat through unchecked development, or will they redesign urban environments to prioritize cooling, resilience, and human well being?

The answer will determine whether future megacities remain livable or become increasingly hostile to the people who inhabit them.