Ondarreta seasonal overview
Best Surf Season (October - March)
Ondarreta's surf year is written by the North Atlantic. From October through March, the storm track across the Bay of Biscay becomes active, cold fronts sweep across northern Spain, and average wave heights sit in the 1.6-2.1m (5-7ft) range with periods pushing 11-13s. The swell window is dominated by WNW/NW/NNW groundswell, and crucially, the wind story flips in your favor: southerly and southwesterly offshores blow on the backside of passing lows a good 41-49% of the time. That combination of long-period Atlantic groundswell and clean offshore airflow is why October through March is the prime window for real quality at this NNE-facing spot.
Fair Surf Season (April - May and September)
April, May and September are transition months. April still sees 1.5m (5ft) average swells at a respectable 10.8s, but the wind starts to back into NNW/NW directions more often, cutting into the clean-window percentage. May loses size and period, dropping to 1.2m (4ft) and 9.9s, but there are still fun, rippable days. September is the standout fair-weather month: the ocean is still warm at 20.9°C, the first autumn lows are forming, and the average period climbs back above 10s.
Low Surf Season (June - August)
Summer brings the Azores High to the doorstep of Northern Spain. The storm track retreats, average wave heights drop to 1.0m (3ft), and periods shorten to around 9s. At the same time, the prevailing airflow turns out of the N, NNE and NNW, which is exactly the wrong direction for Ondarreta's NNE-facing sandbar. Ideal offshore winds drop to just 25-30%. It is longboard season and still fun for beginners, but dedicated surfers know the season truly starts when September turns into October.