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Heat Island Effect | US EPA

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United States Environmental Protection Agency

Heat Island Effect

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  • Heat Island Mitigation Strategies

    How to Keep Your Cool
    Learn about the five strategies to reduce the heat island effect: trees and vegetation, green roofs, cools roofs, cool pavements, and smart growth.
    Learn more>>

  • What Communities are Doing to Reduce Heat Islands

    Communities are Taking Action!
    Find out what state and local entities across the country are doing to reduce the urban heat island effect.
    Learn more>>

  • Heat Island Compendium

    Learn how you can reduce the urban heat island effect in your community.
    Learn more>>

What's New

Learn about equity in heat island mitigation and more in the latest Heat Island Reduction Program Newsletter: April 4, 2019.

Heat Island Effect

The term "heat island" describes built up areas that are hotter than nearby rural areas. The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings. In the evening, the difference can be as high as 22°F (12°C). Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality, and water quality.

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