The story so far:

Delhi and the NCR are facing longer and more intense heatwaves, with the city increasingly retaining heat even at night. Rapid urbanisation, concrete-heavy infrastructure, air conditioning, and shrinking green cover have turned the Urban Heat Island Effect into a deeper “heat re-trap”.

Why is Delhi retaining heat?

This transformation is rooted in the city’s material logic. Concrete, asphalt, steel, and glass dominate Delhi NCR’s expansion. These materials absorb heat efficiently but release it slowly.

Roads, rooftops, and facades accumulate heat through the day and emit it at night, delaying cooling. Surface temperatures in dense areas reach 50-60°C on peak afternoons. These surfaces act as reservoirs, keeping the surrounding air warm well into the night. The city, in effect, stores the sun.

Glass-heavy architecture in areas such as Gurgaon and Noida worsens the problem by allowing solar radiation indoors, increasing reliance on air conditioning rather than reducing heat.

Vehicular activity adds constant thermal input. Corridors like NH-48 function as continuous heat sources, where engines and exhaust combine with heat-absorbing asphalt to create persistent hotspots. Over time, these form into thermal corridors that reshape the city’s microclimate.

At the same time, Delhi struggles to release heat. High-density construction and narrow streets restrict airflow, while traditional cooling features — courtyards, shaded pathways, ventilation corridors — have largely disappeared. As a result, air stagnates and heat accumulates within the city’s form.

How does cooling contribute to warming?

While interiors are cooled, heat is expelled outdoors. In dense neighbourhoods, this raises ambient temperatures by 1-2°C.

This produces a feedback loop: rising temperatures increase the demand for cooling, which in turn releases more heat outside. The city cools itself internally while warming externally.

The energy burden is also significant. Delhi’s peak electricity demand has crossed 8,000 MW during the summer, with cooling accounting for a significant share. Nationally, cooling demand is projected to grow nearly eightfold by 2050, increasing pressure on power systems and raising the risk of outages during extreme heat.

How is heat affecting the economy and ecology?

Factories and warehouses operate within specific temperature limits; excessive heat reduces efficiency and affects machinery. Productivity declines by 2-3% for every degree rise above optimal levels, leading to delays and higher costs.

Supply chains are also slowing as transport hours shrink and storage conditions deteriorate. 

At a broader level, India loses over $100 billion annually due to the decline in heat-related productivity.

Ecologically, the city has lost natural cooling systems. Shrinking green cover, degraded wetlands, and the loss of the Yamuna floodplains have reduced evapotranspiration. Without vegetation and water bodies, Delhi’s ability to regulate temperature has weakened.

What measures are needed to address the crisis?

Addressing this crisis requires structural change in how cities are built and managed. Materials must shift toward high-albedo surfaces, cool roofs, and reflective coatings. Buildings need insulation and passive design strategies like shading and cross-ventilation.

Urban planning must restore airflow through ventilation corridors and better street orientation. Green and blue infrastructure — including urban forests, parks, and water bodies — must expand as essential cooling systems.

Reducing heat generated by human activity is equally important. Sustainable transport, electric mobility, and improved public transit can lower vehicular emissions. Energy-efficient appliances and district cooling systems can reduce heat discharge.

Equally critical is social protection. Affordable housing upgrades, subsidised cooling, and community cooling centres are necessary to protect vulnerable populations during extreme heat.

(Suksham Tanu is a sustainability and environmental studies enthusiast based in Dubai; Amir Hyder Khan is a final-year B.Arch student at Jamia Millia Islamia)