American Council for an Energy-Efficient Economy (ACEEE), June 17, 2014, by Virginia Hewitt, Eric Mackres, Kurt Shickman. (Free registration required to view full report.)
http://www.aceee.org/research-report/u1405

"The urban heat island (UHI) effect is a global phenomenon in which dark, impermeable surfaces and concentrated human activity cause urban temperatures to be several degrees hotter than those in surrounding areas. Urban heat islands impose negative effects on local and global public health, air quality, energy consumption, resilience, quality of life, stormwater management, and environmental justice. Cities across North America experience and mitigate the impacts of UHIs. We conducted a review of the UHI mitigation activities of 26 North American cities and distributed a questionnaire to local government contacts to gather information."