Conditions at Mirleft in September
September: Autumn Begins to Stir
September is the hinge month as Mirleft starts climbing out of the summer lull. Average swell height is still only around 4-5ft (1.4m), but the average period jumps to 10.1 seconds, signalling the return of longer-period Atlantic energy. Swell direction is now NNW at 74.1% with a healthy NW component at 21.3%, and a bigger share of waves reach the 1.5-2.5m (5-8ft) range than in July or August.
Wind remains the limiting factor. NNW is still the most common direction at 30.6%, with NW adding 12.7%, but the pressure gradient is loosening and ideal offshore flow improves to 24% of the time. As the first autumn lows push into the North Atlantic, the quality window grows quickly; late September can produce clean, punchy surf before the big winter swells return. Water temperature peaks at 19.6°C while air averages 22.4°C, making those first good swells feel like a reward after the summer slump.
Average Spot conditions at Mirleft in September
Swell history for September
Wind history for September
Swell quality
Analyze the groundswell consistency at Mirleft 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 Mirleft for your next trip in September.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at Mirleft 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 Mirleft.