Surf forecastStatisticsHistorical report

Cave seasonal overview

Best Surf Season (October - March)

The heart of the North Atlantic storm track aligns perfectly with Cave’s southwest-facing orientation from October through March. Average swell heights climb to a solid 2.0–2.6m, with long-period energy averaging 11–13 seconds. While the dominant swell direction is often from the NW–NNW, the most memorable days arise when deep low-pressure systems track just north of Portugal, pumping powerful SW to W groundswells directly into the bay. Offshore winds from the north through east quadrant (N, NNE, NE, ENE) blow cleanly over the lineup 24–28% of the time, often setting up glassy conditions under clearing skies. This is the prime window for Cave to deliver pumping, firing waves in the 1.5–2.5m range, with occasional XL days pushing well over 2.5m.

Fair Surf Season (April & September)

April and September represent transitional months where the seasonal extremes begin to shift. In April, the average swell drops slightly to 2.0m with a period of 11.1s, but the dominant wind regime starts to shift toward stronger northerly flow. Ideal wind percentages hold at 21%, though the swell direction remains predominantly NW–NNW, limiting the direct hits of optimal SW–W swell. September sees a return of autumn energy: average heights rise to 1.6m and period increases to 10.5s, with ideal wind frequency jumping to 27%. Both months offer fun, rippable conditions on the better days, but consistency and size are reduced compared to the peak winter months.

Low Surf Season (May - August)

From May through August, the North Atlantic storm track retreats northward, leaving Cave with smaller, weaker swell. Average heights hover between 1.4m and 1.7m, with periods dropping into the 8.5–9.9s range. The swell is overwhelmingly dominated by short-period NW–NNW windswell, which struggles to wrap effectively into the SW-facing pocket. Offshore wind conditions are surprisingly frequent during this period, with northerly (N) winds howling 30–44% of the time, but the combination of low period and poor swell direction means waves are often small, weak, and groveling. Only occasional pulse of longer-period W swell can provide brief fun-sized sessions. This is the time for longboards and patience, not for charging.

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Conditions at Cave in September

September: Autumn Stirrings

September is a transitional month with improving swell quality. Average height climbs to 1.6m, period increases to 10.5s—now solidly in the “powerful, long period” range. Swell direction is still dominated by NW (36.0%) and NNW (34.4%), but the W and WSW components start to become more significant (W 4.4%, WSW 1.9%, SW 0.8%). Ideal wind frequency jumps to 27%, as the northerly wind eases slightly (N wind 34.3%). The combination of longer period and more westerly swell angles means Cave begins to see punchy, fun-sized waves with increasing consistency. On the best days, a clean SW groundswell can produce solid, rippable surf.

Average Spot conditions at Cave in September

Swell history for September

0 - 0.5
0.5 - 1
1 - 1.5
1.5 - 2.0
2.0 - 2.5
> 2.5 m

Wind history for September

0 - 10
10 - 20
20 - 30
30 - 40
40 - 50
> 50 km/h

Swell quality

Analyze the groundswell consistency at Cave 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 Cave for your next trip in September.

Ground swell

Ground swell by size

Wind conditions

Evaluate the wind and swell alignment at Cave 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 Cave.

Swell with good wind

Swell with good wind by size