The urban heat island (UHI) effect, especially when considered together with climate change, represents a serious and growing threat to the competitiveness, livability, and inclusiveness of East Asia’s cities. However, because it is a local effect, the leaders of these cities can significantly mitigate its impact on local temperatures while also further promoting greater adaptation to extreme urban temperatures. This World Bank report addresses three critical questions: How strong is the UHI effect in East Asia, and how is it interacting with climate change? Why should policy makers worry about the UHI effect and extreme urban temperatures more generally? What can city leaders do to combat extreme urban heat?