Conditions at Thunders in September
September: Late-Season Consistency with the First Signs of Transition
The Southern Ocean is still firing in September. Average swell height remains at 1.7m (5.6ft), the period stays a solid 14.1s, and the directional split is almost perfectly balanced between S (47.7%) and SSW (47.3%). That is a remarkable amount of usable swell for an Indian Ocean reef break. The size distribution is nearly identical to August: 55% at 1.5-2m (5-6.5ft) and 13.1% at 2-2.5m (6.5-8ft).
Winds are still more SE than anything else, with SE at 37.6% and SSE/ESE at 18.4%/12.9%. But the monsoon transition is beginning. The ideal surfing wind percentage drops to 44%, and you start to see a few more W/NW days as the seasonal pattern drifts back toward the wet season. Rain increases to 7.24mm/day, though water temp holds warm at 28.5°C. Early September often feels like a continuation of July and August; late September can become more weather-dependent. Overall, there are still plenty of high-performance days to be had before the monsoon takes hold.
Average Spot conditions at Thunders in September
Swell history for September
Wind history for September
Swell quality
Analyze the groundswell consistency at Thunders 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 Thunders for your next trip in September.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at Thunders 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 Thunders.