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Extreme weather and climate events have received increased attention in the last years due to their impact on different aspects of human activity. The aim of the present paper is to bring to better understanding of the causes of extreme precipitation occurrence in Bulgaria. An extreme precipitation month is defined as a month registering precipitation totals lower or higher than certain thresholds. Extremely wet months are defined as months with total precipitation amounts higher than 90% percentiles of the gamma distribution in the reference period 1961-1990. As extremely dry month, we consider the month with total precipitation lower than 10% of the gamma distribution. Spatial changes in the occurrence of extreme precipitation are investigated by the application of the cluster analysis. The circulation patterns were analyzed with regard to sea level pressure. The relation between the fluctuations of the extreme months and atmospheric circulation mechanism teleconnection is study by the North Atlantic Oscillation Indices (NAOI), the Eastern Atlantic pattern (EA) and the Mediterranean Oscillation Indices (MOI). [ABSTRACT FROM AUTHOR]