The past 50 years have seen both a quadrupling of global urban population and a rapidlychanging climate, with rising surface temperatures and sea levels and increasing frequencyof extreme weather events. Fast-growing cities—which offer a range of opportunities—cangive rise to a wide variety of stresses, especially if their urbanization is not well-managed.An unpredictable and fast-changing climate compounds these underlying stresses. Theimpacts of climatechange–related shocks on cities may be significant; for many households,they can be devastating. Cities, both small and large, in developing countries sufferdisproportionatelywhen confronted by extreme hot and dry weather events, as well as by tropical cyclones.