- Vegetation is promoted widely all over the world as a means of creating a better quality of life in cities. Plants are credited with lowering air temperature and development of green spaces is considered one of the main strategies for mitigating the urban heat island. This chapter examines the mechanisms by which plants can modify the urban microclimate, with an emphasis on air temperature and outdoor thermal comfort. It outlines a scheme for classifying urban vegetation according to its location in the city and its intended role, which may be useful for planners and landscape architects. The chapter concludes with a methodology for integrating vegetation in the urban planning process to best achieve the desired microclimatic effects.