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Conditions at Sumner Avenue in September
September: Tropical Swell and Long Periods
September is the turning point at Sumner Avenue and often the highest quality month of the year. The average swell height jumps to 1.2m (3.9ft) and the average period stretches to 8.4s - the longest of the year. The swell rose favours E (17.7%), ESE (18.0%) and SE (17.0%), with SSE (11.7%) right behind; the full ESE-S window delivers around 55% of all swell. These are often tropical or early-autumn cold front swells with real power. Winds are mixed: SSW is still common (11.4%), but northerly directions are back, and ideal offshore wind sits at 28%. Water temp is warm at 22.6°C (73°F), air averages 20.7°C (69°F), and precipitation averages 3.17 mm/day. When a hurricane passes offshore and the wind goes NW, Sumner Avenue can be world-class.
Average Spot conditions at Sumner Avenue in September
Swell history for September
Wind history for September
Swell quality
Analyze the groundswell consistency at Sumner Avenue 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 Sumner Avenue for your next trip in September.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at Sumner Avenue 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 Sumner Avenue.