In Algeria, the climatic conditions that have prevailed in the territory for decades have a direct influence on the environment. The aim of this work is to determine the recent evolution of the climate in the Lower Tafna catchment area (North-Western Algeria), by analysing the two periods over a 25-year interval. The study of the different climatic components such as precipitation and annual temperatures during the periods (1913-1938) and (1995-2020) helped us to draw the pluviothermal

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... of Emberger (1955) and the umbrothermal diagrams of Bagnouls and Gaussen (1953), specific to the Mediterranean climate. In terms of average values, temperatures are higher during the new period. Concerning the annual rainfall, the Maghnia station shows a decrease in rainfall while the Beni-Saf station shows an increase in rainfall during the new period. The analysis of the Emberger rainfall climagram (Q2) informs us that the meteorological stations present a certain dynamic during the new period, passing from the upper semi-arid bioclimatic stage with temperate winter to the lower semi-arid with temperate winter for the Maghnia station and the lower semi-arid with warm winter to the upper semiarid with warm winter for the Beni-Saf station. The umbrothermal diagrams show that the duration of the summer season is long and dry, characterised by low average rainfall and high heat.