What causes the heat island effect, and how can it be mitigated in urban areas?

• A. Rural areas cooler
• B. Vegetation effect
• C. Urban areas hotter due to surface materials
• D. Buildings with glass

Answer: (C)

Heat islands form because dense urban surfaces—like dark asphalt and concrete—absorb a lot of solar energy, store it, and re-radiate it as heat. In cities, buildings and street canyons limit ventilation and shade, and there’s less vegetation to provide cooling through evapotranspiration. All of this keeps urban areas hotter than surrounding rural areas, especially at night when the heat has nowhere to go.

Mitigation focuses on reducing heat absorption and increasing cooling. Increasing surface reflectivity with cool roofs and lighter pavements cuts how much heat is absorbed. Adding vegetation, trees, and green roofs provides shade and evaporative cooling. Permeable pavements help water infiltrate and lower surface temperatures, while deliberate urban design—like creating wind corridors and better shading—improves air flow. Improving building energy efficiency also reduces internal heat gain that contributes to the problem.