This study aimed to apply an approach based on fuzzy clustering for the classification of areas associated with soybean yield combined with the following agrometeorological variables: rainfall, average air temperature and average global solar radiation. The study was conducted with 48 municipalities in the western region of Paraná State, Brazil, with data from the crop-year 2007/2008. Through the fuzzy c-means algorithm, it was possible to form groups of municipalities that were similar in soybean yield using the Method of Decision by the Higher Degree of Relevance (MDMGP) and Method of Decision by Threshold β (β MDL). Subsequently, the identification of the appropriate number of clusters was obtained using Modified Partition Entropy (MPE). To measure the degree of similarity for each cluster, the Cluster Similarity Index (ISCl) was constructed and implemented. From the perspective of this study, the method used was adequate, allowing the identification of clusters of municipalities with degrees of similarities between 63 and 94%.