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Nighttime Heat Traps: India's Hidden Urban Crisis
22 May
Summary
- Indoor temperatures in Chennai homes peak at 8-9 PM.
- Lack of overnight recovery dangerously impacts health.
- Cooling gap persists between high and low-income households.
Warm nights are a growing health concern in Indian cities, denying the body essential recovery time. A recent study in Chennai, conducted between October 2025 and April 2026, revealed that indoor temperatures in low-income households often peaked between 8 PM and 9 PM, remaining above 34°C. This persistent heat exposure prevents the body from cooling down, increasing the risk of heat-related illnesses and exacerbating conditions like diabetes and hypertension.
The study highlighted a significant 'cooling gap': high-income households had air conditioning, while low-income households relied only on ceiling fans. This disparity means thermal comfort is out of reach for millions, as building materials like reinforced concrete trap heat long after sunset. This indoor heat exposure is influenced by construction and ventilation, not just outdoor temperatures.
Current Heat Action Plans in India primarily focus on outdoor temperature thresholds and daytime warnings. They largely overlook nighttime temperatures and the needs of those without mechanical cooling. Experts emphasize that India's heat governance needs to expand its scope to include indoor temperatures and the crucial overnight period, where significant health risks accumulate.
