A Global Model for Urban Heat Islands (IMAGE) Princeton University, Engineering School Caption Using summer temperature data from more than 30,000 world cities, researchers developed a new model for urban heat islands that uses population and precipitation as proxies for a complex array of factors involving climate, environment and urban engineering. On the map shown here, cities are marked by colored dots that correspond to the intensity of their urban heat island effect -- red and orange dots indicate cities that are considerably hotter than surrounding areas. Credit Image by Gabriele Manoli. Illustration by Beatrice Trinidad Usage Restrictions Non-commercial use only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.