Urban heat island (UHI) is a phenomenon when temperature in a certain area is hotter than its surrounding areas.  The increasing temperature is not only caused by climate change but it is commonly caused by growing population and rapid urban development due to high levels of urbanization.  As consequences, human activities have elevated the waste heat productions from vehicle combustion, industrial processes, and electricity consumption in particular air-conditioning system.  The circumstances are worsened with land-use patterns in which many new tall buildings were built with limited green space left in addition to the use of asphalt and concrete for land cover. Those are the strongest driver for local air temperatures to rise. Thus, the effects of climate change on rising temperatures will be felt most severely in the urban areas.

Increased temperature because of urban heat island tends to exacerbate the threats to human health, especially heat related illness such as thermal stress, heat cramps, and heat stroke.  The urban heat island can also impact on water availability, quality, and safety. Warmer temperatures may lead to increase demand of clean water while its supply is limited. Additional treatment is required to be used as drinking water. The development of homes using individual groundwater wells and septic tanks can potentially result in an increase in nutrients in surface water or contamination of groundwater due to septic effluent. It is a public health issue.

The cases of urban heat islands are present in some metropolitan cities in Indonesia.  All of them are the capital city, such as Jakarta (capital of Indonesia), Bandung (capital of West Java Province), Semarang (capital of Central Java), Surabaya (capital of East Java), and Bandar Lampung (capital of Lampung). The highest temperature in most of those cities was in high density population areas compared to the business and industrial areas. This means that the contribution of urban heat island in Indonesia could be from the poor settlement of development planning.

Mitigating the urban heat island effects is very important in order to slow down the increased temperature and its bad influence to human life.   Increasing provision of green space, reducing electricity consumption and replacing asphalt with cool pavement should be put in the strategies. The most important thing is how to improve the communities? knowledge and awareness of climate change and its impacts.  Communities need to learn how to adapt with limited sources.  Preventing illness by having a healthy neighborhood environment and preventing communicable disease, and using water and electricity efficiently to reduce waste are a must.