The weather and climate phenomena that produce impact on the cities, and in particular on urban populations, as well as the structure of the urban systems that can influence the climate and meteorology at the local level are analysed. In fact, the large-scale weather systems as well as the climate regime defined as large-scale temporal determine conditions that characterize the city climate, it is known that the structural and morphological changes of the urban fabric, influencing the exchange of energy and matter near the surface, can lead to significant changes of the microclimate.