San Onofre State Beach seasonal overview
Best Surf Season (December - March)
Winter brings the most consistent combination of surf and offshore winds to San Onofre. With the North Pacific storm track firing on all cylinders, long-period groundswells from the W and WSW dominate, averaging 1.0-1.1m at 12.4-12.6s. While these swells aren't always perfectly aligned with the optimal S-SW window, the angles from WSW and W wrap nicely into the point. The real key is the wind: offshore flow from the N through ENE blows over 50% of the time in December and January, grooming the waves to perfection. The occasional Southern Hemisphere swell adds variety. This is the prime window for clean, rippable waves at San O.
Fair Surf Season (April, May, October, November)
Spring and fall offer transitional conditions. In spring, the south swell season begins to show life — April and May see increasing amounts of SW and SSW swell with longer periods (13.3-13.5s). However, the offshore wind window narrows dramatically (19% in April, 8% in May) as the Pacific high strengthens and onshore afternoon breezes become more frequent. Early mornings can still deliver clean waves before the wind kicks up. October and November see a reversal: offshore winds increase again (30% in Oct, 45% in Nov) as the high shifts, but swell from the W and WSW is still solid, though period drops slightly. These months provide a good balance but require picking the right tide and wind window.
Low Surf Season (June - September)
Summer is the most challenging time for consistent surf at San Onofre. While the southern hemisphere pumps out consistent long-period SW and SSW swell (periods 13.6-13.8s, heights around 1.0m), the onshore wind pattern dominates. The wind is ideal only 6-9% of the time, with persistent W and WSW winds creating choppy, bumpy surfaces. Despite the swell size being fun-sized, the poor wind conditions limit quality sessions to rare early morning offshore windows or when tropical systems align. It's a season for the dedicated dawn patrol and the occasional typhoon-swell winner.
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Conditions at San Onofre State Beach in September
September: Transition to Better Winds
September marks the beginning of the transition back to better wind conditions. Ideal wind jumps to 18% as the Pacific high weakens. Swell heights hold at 1.0m with long periods of 13.6s. SW (41.8%) and WSW (34%) swells remain dominant, with some SSW (16%). The combination of improving winds and solid swell makes for some of the best late-summer setups. Early autumn can deliver classic San O conditions.
Average Spot conditions at San Onofre State Beach in September
Swell history for September
Wind history for September
Swell quality
Analyze the groundswell consistency at San Onofre State Beach during September. Based on historical data, there is a % probability of groundswell occurring this month. The chart below provides a detailed breakdown of the average wave height distribution, offering deep insights into the swell quality and surf potential you can expect at San Onofre State Beach for your next trip in September.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at San Onofre State Beach for September. Our analysis shows that favorable offshore or side-shore winds coincide with surfable swell approximately % of the time. The accompanying graph illustrates the average size distribution of waves during these optimal wind windows at San Onofre State Beach.
