Sines in Portugal is a powerful and consistent surf spot, with the best conditions typically found during the winter months when ground swells dominate and wave heights are at their largest. From October to March, ground swell averages between 67% and 92%, providing clean, well-organized waves, with mean swell sizes ranging from 1.8m to 2.4m. The most consistent swells occur from December to February, when ground swell percentages peak above 85%, and mean swell sizes exceed 2.3m, making these months ideal for advanced surfers seeking powerful waves. Wind conditions are less favorable in winter, with good wind days only occurring around 30% of the time, meaning onshore winds are frequent. However, the strong, clean ground swells often compensate for wind interference. Spring and summer (April to September) see a significant drop in ground swell dominance, shifting toward wind swells, which become more prevalent from May onward, peaking at 84% in July. Wave heights diminish to around 1.3m–1.5m in these months, making conditions better suited for intermediate or beginner surfers. Wind conditions improve slightly in summer, particularly in August and September, where good wind days reach 39% and 44% respectively, offering more offshore opportunities despite the smaller, less consistent swells. For the best balance of swell power and manageable winds, October and November can be a good transition period, with decent ground swell presence (67%–76%) and slightly more favorable wind conditions compared to mid-winter. Overall, the prime surfing window in Sines is from late autumn to early spring, with December to February delivering the most powerful and consistent waves, despite the challenging wind patterns.