An urban heat island is when urban areas experience significantly higher temperatures than the surrounding rural areas. Urban building materials like concrete and asphalt absorb and retain heat from the sun, causing cities to be warmer, especially at night. Urban heat islands are intensified by dense concentrations of buildings and paved surfaces, and by reduced vegetation, such as trees.
  
Trees provide shade, reducing the sun’s heat reaching buildings and pavement, which lowers surface and air temperatures.
  
Trees release water vapor into the air through a process called evapotranspiration, which cools the surrounding environment.
 
By cooling the air and absorbing pollutants, trees improve overall urban climate conditions, making cities more livable.
  
By shading surfaces and adding moisture to the air, trees play a critical role in combating the urban heat island effect and creating a healthier New York City.
  
Our tree planting projects, like Greening the Bronx and Trees for NYCHA, are designed to shade and cool urban heat islands. We plant large shade trees to shade heat-absorbing surfaces such as walkways, parking lots, buildings, and paved playgrounds.