Cities alter the climate system both within their boundaries and nearby through interactions with dark, built-up, and impervious land surfaces, energy generation, and dense networks of roads and automobiles. These processes that occur on urban scales are interacting with larger-scale climate change processes to exacerbate extreme events that impact city and metropolitan region dwellers. This Element assesses the latest research on urban heat and precipitation islands, compound extreme events, and indicators and monitoring, including the use of ground based observations, remote sensing, and citizen science in urban settings. It provides temperature and humid heat index, precipitation, and sea level rise observations and projections for the cities engaged in ARC3.3. The Element emphasizes the importance of co-generating urban climate risk information to form the best-available foundation for climate adaptation and mitigation actions in cities. This title is also available as open access on Cambridge Core.