Ondarreta - surf spot statistics

Best Surf Season (October - March)

The North Atlantic delivers its best to Ondarreta from October through March, when the average swell height climbs above 1.6m and wave periods frequently exceed 11 seconds. During this window, the region benefits from powerful extratropical storms tracking across the Atlantic, sending long-period NW and WNW swell directly into the beach's N-NE facing orientation. Offshore winds from the S and SSW quadrant blow cleanly 44-49% of the time, groomed by a semi-permanent high-pressure ridge over the Iberian Peninsula. The combination of consistent, punchy surf and favorable wind regimes makes this the prime window for Ondarreta's best quality waves.

Fair Surf Season (April & September)

April and September serve as transitional months, offering a mixed bag of conditions. April sees the average swell height drop to 1.5m with periods around 10.8s, while September brings a slight uptick to 1.3m and 10.4s. During these months, the wind is ideal roughly 37-38% of the time, as cold fronts from the north begin to weaken or intensify. Swell direction remains predominantly from the NW and WNW, but shorter-period windswell becomes more frequent. While not as consistent as the peak season, these months can still produce fun, rippable waves when the right setup aligns.

Low Surf Season (May - August)

From May through August, Ondarreta experiences its low season, with average swell heights hovering around 1.0m and wave periods dropping to 8.8-9.9s. The wind becomes less reliable, with ideal offshore conditions dropping to 25-36% of the time. The dominant wind shifts to onshore from the N and NNW, which directly degrades wave quality. Combined with smaller, shorter-period swell, the surf is often small and choppy. However, even during these months, occasional pulses of longer-period NW swell can bring fun-sized waves, especially in the late afternoon when sea breezes sometimes offer a brief window of cleaner conditions.

March: Late-Winter Power

March continues the winter pattern but with a slight drop in average swell height to 1.8m and period to 12.1s. The NW direction accounts for 37.5% of the swell, offering robust, clean lines. Ideal wind conditions occur 41% of the time, with S (11.5%) and SSE (9.2%) being the primary offshore contributors. The waves are often in the fun to solid range (1-1.5m and 1.5-2.5m), but the period remains long enough to provide excellent shape. Look for days when a high-pressure ridge stalls over the Bay of Biscay, reinforcing the offshore flow.