The study of climatic conditions in Buenos Aires city has a great importance because of the people living in it. Extreme temperatures present a major impact on the supplying of services which implies the necessity of a diagnosis for various applications. The temperatures series of Buenos Aires Central Observatory have been chosen for this study, for their quality and it have been verified that they represent a large area of influence covering a zone larger than the city. The records used in this work, on some scales cover from mid-nineteenth century up to now and especially from 1909 to 2013 in a daily scale. The evolution of temperatures throughout the century is studied, focusing mainly on the cold periods. A natural state corresponding to the first 20 years of record series is defined where both series do not show a significant linear trend. The cut-off values are defined based on he natural state for studying the different properties of cold semesters. The duration of these as to the maximum temperatures experienced a decrease of 30 days, whereas in the minimum temperatures, of 53 days. The amplitude of the annual harmonics present variations, in the maximum temperatures a negative linear trend is observed, while in the minimum temperatures it is positive. These results are showing the existence of inter-annual variability of the intra-annual variability. The analyses made on the centenarian series allow to reconstruct them as a natural state or an anthropogenic state.