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An attempt is made to find the main monthly modes of variation of precipitation over the Iberian Peninsula. The modes of variation of precipitation were derived from principal component analysis. The dataset used consists of records of monthly precipitation from 40 meteorological stations over 74 yr (1919--92). The stations are spatially representative of most of the Iberian Peninsula. To take into account the seasonality of precipitation over the Iberian Peninsula, one analysis was performed separately for each calendar month. The modes of variation resulting from the different analyses were compared and clustered in groups according to their loading patterns. Seven main patterns were found to be of importance during various months of the year. These seven patterns explained more than 75% of the variance of the precipitation field from December to April. However, less than 20% of the total variance is explained for July and August. It is concluded that, depending on the month or season of interest, different modes of variation should be considered in order to achieve a better description of the monthly precipitation field. [ABSTRACT FROM AUTHOR]