Relevance: GS Paper III (Environment & climate change; disaster management) and GS Paper I (urbanisation) | Source: The Indian Express (Explained)
As a harsh heatwave grips India — Piduguralla (Andhra Pradesh) touched 47.6°C and the monsoon is set to reach Kerala by 26 May — an Indian Express analysis warns of a quieter danger: hotter nights, which may harm health even more than hot days.
1. What the news says
- Cool nights let the body recover. When nights stay hot, there is no relief, especially in small, poorly ventilated homes.
- India is about 0.7°C warmer (1901-2018). By 2100, days may rise 4.7°C but nights may rise 5.5°C — so nights are heating faster.
- A Climate Trends study in Chennai found people sleeping above 32°C, sometimes 35°C.
- The Urban Heat Island (UHI) effect: concrete and roads soak up heat by day and release it at night, so city centres stay 4-6°C hotter than the outskirts.
Fig: The classic urban heat island shape — the city core stays hottest at night (schematic).
2. Why hot nights are dangerous
- In Ahmedabad, daily deaths rise from about 100 to 265 when the night temperature crosses 30°C.
- Most Heat Action Plans (HAPs) — in 23-plus states — focus only on declared heatwaves, not everyday extreme heat.
- The poor, outdoor workers and the elderly suffer most. Ahmedabad’s 2013 HAP was India’s first.
UPSC Value Box
| Term / Provision / Body | Simple meaning & how it is used |
| Urban Heat Island | A city much hotter than nearby villages because of buildings, roads, vehicles and waste heat. |
| Heat Action Plan (HAP) | A city/state plan with warnings, cooling shelters, changed work hours and long-term steps. |
| Wet-bulb temperature | Heat plus humidity together; values near 35°C for long can be deadly for the body. |
| Passive cooling | Cool/white roofs, shade and air-flow that cut indoor heat without using power. |
3. The way forward
- Update HAPs to cover heat that is round-the-clock and indoors, not just declared heatwaves.
- Spread cool/white roofs, green cover and water bodies; use building codes like the Eco-Niwas Samhita.
- Provide cooling shelters, ORS and shifted work hours; consider making heat a notified disaster.
Conclusion: As cities grow and the planet warms, India must treat heat as an all-day, indoor and night-time threat — the key to safe, climate-ready cities.
UPSC Mains Practice Question
- “Rising night-time heat and the urban heat island are turning Indian cities into health hazards.” Suggest steps to build urban heat resilience. (15 marks, 250 words)
Answer hints:
- Intro: The focus shifts from daytime heatwaves to deadlier hot nights.
- Body: How UHI works, Ahmedabad death data, gaps in Heat Action Plans, who suffers most.
- Value-add: Ahmedabad HAP 2013, cool roofs, wet-bulb temperature, Eco-Niwas Samhita.
- Conclusion: Treat heat as a disaster; design cooler, fairer cities.
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