Prelims fact sheets
Urban Heat Island Effect: UPSC Prelims Fact Sheet
An urban heat island (UHI) is a city area that is significantly warmer than nearby rural areas, mainly because concrete, asphalt and buildings absorb and re-radiate heat, vegetation is scarce and human activity releases waste heat.
Pragnya IAS Academy, Hyderabad · Updated 16 October 2026 · 5 min read
Key facts
| Item | Detail |
|---|---|
| Main causes | Low albedo surfaces, loss of green cover and water bodies, waste heat from vehicles and ACs, dense buildings trapping heat |
| Peak effect | Night-time, when stored heat is released |
| Impacts | Heat stress and deaths, higher electricity demand, poor air quality, water stress |
| Mitigation | Cool / reflective roofs, urban forests, green roofs, restoring lakes, heat action plans |
| Indian example | Ahmedabad Heat Action Plan (2013), Telangana Cool Roof Policy (2023) |
Why it matters for UPSC
- GS 1 urbanisation and GS 3 disaster management (heatwaves are a notified concern under state disaster plans).
- Hyderabad's lake loss and rapid built-up growth are useful local examples for Mains answers.
- Links to climate adaptation and sustainable cities (SDG 11).
Prelims angle
Expect statement questions on albedo, why the effect peaks at night, and mitigation measures. Albedo is the fraction of solar radiation reflected — light surfaces have higher albedo.
Frequently asked questions
Why is urban heat island effect stronger at night?
Concrete and asphalt store heat during the day and release it slowly after sunset, while rural areas cool faster.
What is a cool roof?
A roof coated or built with reflective material that raises albedo and reduces heat absorbed by the building.