Heat Island Effect

Heat islands occur when urban areas experience higher levels of thermal heating than adjacent exurban and rural areas. Cities that maintain a higher average temperature than their surroundings can be viewed as islands of heat surrounded by cooler, nonurban landscapes. Around the world, many cities maintain air temperatures up to 10 degrees F (5.6 degrees C) warmer than surrounding areas. Scientists, urban planners, and historians are beginning to recognize that urban heat islands are [Page 858]not simply inconsequential environmental phenomena. Rather, the effects of urban heat islands are now being linked to processes of urban economic development and to levels of individual and community vulnerability.

Urban areas contain distinct physical properties that contribute to higher surface temperatures. The conversion of formerly vegetated landscapes to nonvegetated surfaces ...