The identification of weather patterns and associated surface waves for the Southwestern Atlantic Ocean is the goal of the present work. For this purpose, a K-means algorithm was adopted to group data into similar atmospheric conditions considering 25 years of reanalysis data (1993-2017) of zonal and meridional wind components and geopotential height at 1000 hPa. Three points (Vitoria, Santos and Rio Grande) along the Brazilian coast were chosen to evaluate the wave extremes and which Weather Patterns are associated with the extremes in these three different regions. The knee point detection method was used to determine the ideal number of centroids for representing the Weather Patterns at each point. The dates corresponding to each WP were used to plot the average wave field associated with each WP. The results indicate that WPs are dominated by both cyclones and anti-cyclones in the domain. Cyclones with a south/southwest fetch induce extreme waves in Santos and Rio Grande, while for Vitoria, extreme wave generation is more dominant due to the influence of the post-frontal high.