Urban heat islands refer to zones of high temperatures that result from concentrated structures or limited greenery. This is caused by reduced natural landscapes, the complex geometry of urban landscapes (blocking ventilation and regular air movement), human activities, and urban materials. All of these factors are exponentially magnified when high populations of people move into a compact space, as often shown in large cities. This creates an urban heat island that has higher temperatures, resulting in stronger local warming. Beyond the discomfort of higher temperatures, problems of fires and reduced mental health are at play. Furthermore, the populations in urban environments are often of low socioeconomic status and cannot easily relocate. 

In cities, the urban heat island poses a challenge towards many people as warmer city conditions adversely harm residents. Whether change is provided through new materials, influenced human activity, or efficient city design, the urban heat island is a large challenge for larger metropolitan areas.