Chennai heating faster than rest of TN

CHENNAI: A new State government report has confirmed what Chennai residents have long felt: The city is getting hotter, and it’s not just because of the sun.

According to the Decadal Assessment of Urban Growth and Thermal Stress in Tamil Nadu (2025), Chennai is among 25 blocks in Tamil Nadu that faces both long-term heat rise and extreme present-day heat stress. The report squarely links this to uncontrolled urbanisation, vanishing green cover, and poor land planning.

Between 1985 and 2015, the city’s built-up area grew from 48% to 74%, meaning nearly three-fourth of the land is now covered by concrete, asphalt, or buildings. These surfaces trap and re-emit heat, especially at night, worsening what scientists call the Urban Heat Island (UHI) effect.

Data from satellite-based thermal sensors show that night-time Land Surface Temperature (LST) in Chennai and its surrounding blocks has risen by 3-4°Celsius over 20 years. Night-time heat prevents the body from cooling down, increasing the risk of heatstroke, sleep loss, and chronic illness, particularly for elderly and low-income residents.

The report notes that 35% of the city’s urban population lives in slums, where homes are often made of heat-absorbing materials like tin sheets and cement slabs with little tree cover or cross-ventilation. The report advises to create more green and blue infrastructure such as parks, lakes, green roofs, shaded streets.

Introduce ‘cool roof’ materials in low-income housing (especially in TNHB schemes). Enforce zoning laws to curb heat-intensive development in overbuilt zones like Villivakkam, St Thomas Mount, and Poonamallee. Integrate heat stress indicators into Smart City plans and storm water projects. Prioritise high-risk blocks for tree plantation and public cooling zones.

The Tamil Nadu Heat Mitigation Strategy (2024) already calls for such measures, but implementation has been slow. With summer heat waves worsening leading to 12 heat-related deaths reported in TN in 2023, the report urges the Chennai Corporation to treat heat as a core governance issue, not just a seasonal one.

Suggestions in the report

· Create more green and blue infrastructure such as parks, lakes, green roofs, shaded streets

· Introduce ‘cool roof’ materials in low-income housing (especially in TNHB schemes)

· Enforce zoning laws to curb heat-intensive development in overbuilt zones like Villivakkam, St Thomas Mount, and Poonamallee

· Integrate heat stress indicators into Smart City plans and storm water projects

· Prioritise high-risk blocks for tree plantation and public cooling zones

Most heat-stressed blocks in TN

Chennai

St Thomas Mount (Chengalpattu)

Poonamallee (Tiruvallur)

Villivakkam (Tiruvallur)

Puzhal (Tiruvallur)

SS Kulam (Coimbatore)

Sulur (Coimbatore)

Periyanaickenpalayam (Coimbatore)

Tirupur

Palladam (Tiruppur)

Tiruparankundram (Madurai)

Mandapam (Ramanathapuram)

Tiruverumbur (Tiruchirappalli)

Salem

Erode

Karur

Kundrathur (Kancheepuram)

Thoothukudi

Dindigul

Kodaikanal (Dindigul)

Vellore (Vellore)

Sivaganga (Sivaganga)

Villupuram (Villupuram)

Poonamallee (Tiruvallur)

Periyanaickenpalayam (Coimbatore)