Beach break de arena · Cantabria · 31-year record (1995–2025)
Marine model forecast from Open-Meteo, refreshed when the page loads.
Four slots a day with groundswell height and period, wave energy in kilojoules and the wind classified against the orientation of Somo.
| Day | Slot | Height | Period | Direction | Energy | Wind | Rating |
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← Swipe the table to see every column →
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Height alone is misleading. A metre and a half of swell at twelve seconds carries far more water behind it — and breaks with far more force — than a metre and a half at six seconds, even though both read the same in a forecast. What measures that difference is wave energy: what a whole wave carries per metre of crest, expressed in kilojoules.
It comes from E = ρg²/(32π) · H² · T², so it grows with the square of the height and the square of the period — which is why a long groundswell hits so much harder than a short windswell of the same size. As a reference, below 100 kJ it is small; 100 to 300 works for a longboard; from 300 kJ there is plenty of push for a shortboard; and past 1,000 kJ the sea starts to get serious.
At Somo the historical mean is 328 kJ and one day in ten exceeds 845 kJ; the record in the series is 12,086 kJ. The most powerful month is February at 704 kJ, and the weakest July at 68. The forecast above gives the value for each slot.
If you prefer the unit used in oceanography, mean wave power here is 13.3 kW per metre of crest. It measures something different — energy per second rather than per wave — so the period counts for less.
Share of hours in each month with surfable sea, with good surf — enough swell and favourable wind —, mean height and mean wave power. Tap to switch indicator.
Across the 271,752 hourly reanalysis records, 55.6 % of the swell reaching Somo comes from the NW. Median height is 1.24 m and mean period 9.0 s; one day in ten the sea tops 2.6 m.
Surfable sea — at least 0.8 m and an 8 s period — occurs 59 % of the time over the year, peaking in February (83 %) and bottoming out in July (26 %).
Wind is what separates a good day from a wasted one. At Somo the swell arrives from the NNW, so the wind blows offshore — the one that grooms the wave — when it comes from the SSE. That happens 20 % of the hours in the year. Add 32 % of glassy hours, below 8 km/h, and the air is in your favour 52 % of the time.
Against you: 27 % of the time the wind blows onshore and messes the wave up. The most repeated direction of the year is W. On average there are about 29 hours a year with wind above 40 km/h, concentrated in the winter storms.
Both roses carry a marker on the rim showing what suits this spot. Somo faces NNW (330°), so clean swell only enters from W to NE — the blue arc. The dominant swell direction is NW, with 56 % of the hours in the year, and it falls squarely inside that window, which is why the spot is rarely flat.
Wind works the other way round: the good one blows from land to sea, holding the wall of the wave up and grooming it. Here that is the wind from E to SSW, the green arc. The red one is onshore, arriving from sea to land and messing up the surface: W to NNE. The most frequent wind of the year is from the W.
Each spoke points to the direction the swell or wind comes from, and its length is the share of hours. The scale is square-root, as is standard for roses, so small sectors do not vanish next to the dominant one.
Somo is the long beach you see from Santander across the bay, reached by the ferry from Puerto Chico. Its wave is among the friendliest on the Cantabrian coast: sand bottom, gentle gradient and peaks spread over several kilometres, with El Puntal at one end producing long, soft rights when the swell comes in big. It is where half of Cantabria learns to surf.
Sea temperature forecast for the coming hours: –.
The statistics on this page are not estimates: they are computed over 271,752 hourly records from the ERA5 reanalysis between 1995-01-01 and 2025-12-31, 31 full years. ERA5 is the atmospheric reanalysis of the European Centre for Medium-Range Weather Forecasts, and its ocean component reconstructs the state of the sea hour by hour by combining the wave model with every available observation.
Wave data comes from the ERA5-Ocean model and 10-metre wind from atmospheric ERA5, both served by Open-Meteo. The next seven days come from the operational marine model, which is a different thing: a forecast, not a record.
Two limits worth keeping in mind. First, the model describes the open sea, and what the wave does when it meets the specific bottom at Somo — the bank, the reef, the tide — is not in these numbers. Second, model resolution is several kilometres, so on deeply indented coastlines the grid point can sit some way from the peak. Always check the local report before paddling out.
