As a result, the city's climate is considered subtropical, with average temperature during the year at around , rarely exceeding in summer. In winter the average is . Topography The landscape of Mauá is dominated by the formation of steep hills and peaks, as it is the usual Serra do Mar landscape, and by deep valleys and wetlands, today mostly grounded and occupied in a disordered way, which explains the high incidence of flooding there. Only the valley of Tamanduateí River on Capuava district is typically flat. Historical account describe the place as where the first bandeirantes, coming from São Vicente, saw the Planalto Paulista (São Paulo plateau) region and gave the name of Borda do Campo (that means Boundary of the Countryside) to the region, for making the transition between the Serra do Mar and the Planalto Paulista. The highest point in town is the Morro Pelado (Naked Hill), with 867 meters (the third highest of the Greater São Paulo), but the city is, on average, the highest of metropolitan region, due to the lack of flat areas. Hydrography The city has a special characteristic hydrographic: not be crossed by any water course from another city, since, due to the high altitude, all streams that cross the territory of Mauá has their sources inside the city limits. In the city is located the source of Tamanduateí River, the third largest affluent of the Tietê River in Greater São Paulo, the Oratório river and the Pinheirinho and Guaió rivers. The most important waterways in the urban area are the Taboão Stream, the Corumbé Stream and the Capitão João Stream (which flows under the XXII de Novembro square, in the downtown). Due to the disordered occupation of the floodplains, many places that before acted as absorbers of excessive rain water were grounded and the city has several points at high risk of flooding. The situation was eased with the construction of four reservoirs between the years 1998 and 2002. However, due to lack of maintenance, excessive garbage and siltation, the reservoirs can not effectively avoid the flooding risk. Besides the disordered occupation, lack of sewerage and waste treatment makes the urban waterways completely polluted. Vegetation The city, due to great variation in altitude has a broad spectrum of natural landscapes, although much has been transformed by human occupation. The hillsides were originally occupied by a lush Atlantic Forest, though already mixed