Conditions at Crab Island in September
September: The Autumn Awakening
September is a genuine turning point. Average swell height climbs back to 5ft (1.5m), and the period lengthens to 10.2 seconds, signalling the return of real groundswell. The swell direction data shows a strong and consistent W contribution of 37.0%, with WNW at 21.9%, WSW at 17.1%, and NW at 4.2%, giving over 80% of swell from the optimal quadrant. There is a solid distribution of 1-2.5m (3-8ft) waves, and the frequency of rideable, lined-up surf jumps noticeably.
Wind quality also improves from the summer low: ideal conditions run at 17%, with offshore ENE-to-SE flow around 17.2% and the onshore westerly sector at 36.2%. While the classic Atlantic west wind is still common, the stronger late-summer high pressure systems can set up beautiful morning offshore flows. Water temperatures remain comfortable at 15.7°C, air averages 13.9°C, and precipitation stays moderate at 3.40mm/day. This is the grace period of the Irish surf season: proper swell, warmer water, and more clean days.
Average Spot conditions at Crab Island in September
Swell history for September
Wind history for September
Swell quality
Analyze the groundswell consistency at Crab Island 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 Crab Island for your next trip in September.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at Crab Island 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 Crab Island.