The objective of this research was to study the rainfall variability in the South of Brazil in terms of homogeneous areas for extreme events. It was applied the K-means algorithm (cluster) and the Regional Frequency Analysis technique to a daily time series of precipitation data from the National Water Agency (ANA) (1981-2010). The results indicated 8 precipitation homogeneous regions and in each of them can occur extreme precipitation events exceeding at least 100mm daily.