Mejillones, Spain, offers surfable conditions year-round with a mix of ground swells and wind swells, though the best months for quality waves are typically during the winter and early spring. From January to April, the swell consistency is excellent, with ground swells dominating (76–93% of the time) and mean swell sizes ranging from 1.9 to 2.1 meters, providing powerful, clean waves. However, wind conditions during these months are less favorable, with only 23–34% of days offering good offshore or light winds. November and December also see strong ground swells (90–91%) and decent swell heights (2.0 meters), but the wind remains problematic, with high chances of onshore or strong winds (64–77% bad wind days). The summer months (May to August) experience a shift toward wind swells, which are less consistent and generally smaller (1.3–1.6 meters), though the wind conditions improve, with July and August offering the best chance of favorable winds (42–43% good wind days). September and October bring a transition back to better swell conditions, with ground swells increasing again (54% in September, 79% in October), but the waves remain smaller (1.3–1.6 meters) and wind reliability is moderate (35–36% good wind days). The optimal window for surfing Mejillones is from February to April, when ground swells are most consistent and wave heights peak, despite the higher likelihood of unfavorable winds. Advanced surfers may prefer these months for the larger, cleaner waves, while beginners or those seeking lighter conditions might find summer more manageable, albeit with smaller, less powerful swells. Late autumn and early winter (November–December) also deliver strong swells but require patience due to frequent poor wind conditions.