Resumen
Abstract: In southern South America and for the period 1960-2011, frequencies and trends of seasonal blocking situations (Bs) determined at 100º, 70º and 40ºW (B100, B70 and B40) are estimated. The effect of such situations on temperature and precipitation is also analyzed. The distribution of occurrences of B100, B70 and B40 peaks in spring and has minimum values in summer; trends are positive in summer and fall and negative in winter and spring.To the north of approximately 38ºS, B70 determine negative temperature anomalies (DT) over the entire country during the four seasons and B40 in spring and summer. Except for summer, rainfall is greater than normal when Bs occur at both longitudes.To the south of approximately 38ºS, B100 give place to negative DT. The frequencies and amounts of precipitation are greater in spring. This area is limited to the northernmost northern (southernmost southern) area in fall (summer).According to the signs of the trends of the Bs and to the associated values of temperature and precipitation, it is inferred the way in which they may have contributed to the change in both variables during 1960-2011.