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Conditions at San Onofre State Beach in September
September: Tropical Energy and the First Fall Hints
September is the hinge month on the Southern California coast. The average swell height recovers slightly to 3.3ft (1.0m) and the period holds at a strong 13.6s. Swell direction is again dominated by SW 42%, WSW 34%, and SSW 16%, with only 8% from W. The presence of SSW energy reflects the tropical cyclone belt and early-season southern hemisphere swells; when one of those pulses lines up, San Onofre will see some of the most favorable, straight-in wave angles of the year.
Wind is better than summer but still not great: ideal conditions rise to 18%, taking the edge off the persistent onshore flow. Onshore S through WSW winds still account for 35%, and the westerly sea breeze remains prominent, but there are more morning windows with light northerly drainage. Water temperature peaks at 18.2°C, air temperatures hold around 22.4°C, and precipitation is still scarce at 0.17 mm/day. September rewards those who watch the tropical outlook and get up early.
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.