Urban Heat Island (UHI) Effect

Urban Heat Island (UHI) Effect


Urban areas trap more heat due to altered thermodynamic and aerodynamic properties, resulting in significantly higher temperatures compared to rural areas.


GS-03 (Environmental pollution and degradation)


  • Rising global temperatures and frequent heatwaves exacerbate the warming effects in cities, intensifying urban heat challenges.
  • The expansion of concrete structures, roads, industries, and residential areas contributes to additional urban warming.
  • Urbanisation alters local heat distribution patterns, affects rainfall distribution, and exacerbates air pollution, impacting public health.
  • Increased urban temperatures lead to heat-related illnesses and higher mortality rates, stressing the need for effective heat management.
  • Elevated temperatures put additional stress on urban infrastructure, particularly cooling and energy systems, and contribute to the degradation of green spaces and water bodies.
  • Tier-II cities in eastern India experience more urbanisation-driven warming compared to larger metros, highlighting the uneven impact across different urban areas.

Urban Heat Island?

  • Urban heat island refers to local and temporary phenomena where certain city areas experience higher heat loads than surrounding regions.
  • Heat Trapping in Concrete Structures: The rise in heat is primarily due to buildings and houses made of concrete, which trap heat and prevent its easy dissipation.
  • Temperature Variation: The temperature difference between urban heat islands and their surroundings can range from 3 to 5 degrees Celsius.


  • Construction Activities: Increased urban construction using heat-absorbing materials like asphalt and concrete raises mean surface temperatures in cities.
  • Dark Surfaces: Urban buildings often have dark surfaces that lower albedo, leading to increased heat absorption.
  • Air Conditioning: The use of air conditioning in buildings with dark surfaces requires more energy and causes further local heating, creating a cascade effect that expands urban heat islands.


  • Increase Green Cover: Planting trees and increasing green areas help reduce heat load within urban regions.
  • Passive Cooling: Implementing passive cooling technologies, which naturally ventilate buildings, can mitigate the urban heat island effect.
  • Heat Mitigation Materials: Using appropriate construction materials, painting roofs and terraces in white or light colors, and promoting terrace plantation and kitchen gardening can help reduce heat absorption and urban temperatures.