What 43° North Actually Means for a Surfer

In December the sun comes up over Donostia at about half past eight. By the time it clears the hills behind the bay it’s closer to nine, and if you have a job, you’ve already missed the good part. In June that same sun is up before half past six and still hanging around at ten in the evening.

Same beach. Same water. Same 43rd parallel. The only thing that changed is where the planet is pointing.

I’ve been drawing daylight for years — the Circular Calendar is really nothing but a year of sunshine hours bent into a ring. What I didn’t expect was how differently that same data reads once you start planning your week around waves.

The surf year runs backwards

Here’s the part nobody mentions when they tell you the Basque coast has great surf.

The North Atlantic does its serious work between October and March. That’s when the low-pressure systems track across from Newfoundland, when the swell arrives with period behind it, when the waves are actually worth the drive. It is also, precisely, when the light is gone.

Summer is the opposite deal. Fifteen hours of daylight and, more often than not, knee-high mush.

So the surf year is inverted: the window is widest when there’s nothing to use it for, and narrowest when it matters. Everyone who surfs north of about 40° lives with this. Most of us never put a number on it.

Six hours and twenty minutes

That’s the spread at 43° North — the difference between the longest day of the year and the shortest.

Spot	Latitude	Shortest day	Longest day	Spread
Thurso, Scotland	58.6°N	~6h 20m	~18h 20m	12h 00m
Donostia, Basque Country	43.3°N	~9h 00m	~15h 20m	6h 20m
Ericeira, Portugal	39.0°N	~9h 25m	~14h 50m	5h 25m
Taghazout, Morocco	30.5°N	~10h 10m	~14h 05m	3h 55m

Thurso is the interesting one. Some of the best cold-water waves in Europe break there, and in late December the surfable day is barely six hours long — while in June it never really gets dark at all. Twelve hours of swing. (If you want to see how that scales further up and down the globe, we went through it city by city in Cities on Latitude 60, 50, 40 Degrees North.)

Move south and the year flattens out. Taghazout loses under four hours between solstices. Part of why Morocco fills up with European surfers every winter isn’t just the water temperature — it’s that the day doesn’t collapse on you.

Your clock is lying, and here it lies badly

There’s a second thing going on at this particular spot, and it took me embarrassingly long to notice.

San Sebastián sits at about 2° West. Geographically that puts it in the same solar time zone as Lisbon or London. Spain runs on Central European Time anyway — a decision from the 1940s that nobody has got round to undoing.

The result: solar noon here lands around ten past one in winter, and after two in the afternoon once the clocks go forward. The sun is at its highest when your phone says it’s mid-afternoon.

For a calendar this is a curiosity. For planning a session it’s a real offset. “I’ll go around noon” means something quite different from what the sky is doing.

Why the short days are better than they look

Now the part that redeems winter.

The reason dawn is the good slot has nothing to do with crowds and everything to do with temperature. Overnight, land loses heat faster than water. The air above it gets denser and drains seaward — an offshore breeze that holds the wave face up and grooms it clean. Then the sun comes up, the land heats, the air over it rises, and the sea breeze turns around and blows onshore. The surface goes to chop. Anyone who has watched a good morning fall apart by eleven has watched this happen.

But that cycle is powered by the sun. In December, at this latitude, the sun is low, weak, and out for nine hours. It often never manages to build a proper sea breeze at all.

Which means: a winter day here gives you fewer hours, but a larger share of them are clean. A June day hands you fifteen hours and takes the best of them back by late morning.

Short doesn’t mean worse. It means concentrated.

Worth saying plainly — this only holds when the weather is otherwise quiet. A deep low parked in the Bay of Biscay drives its own wind and doesn’t care what the sun is doing. Thermal effects are the default, not the law.

What I ended up building

Once you start thinking this way, most surf forecasts look slightly wrong. They hand you twenty-four hours of data, including a beautiful three in the morning that no one will ever surf.

So I built one that doesn’t. Surflogbook draws each day’s forecast across that day’s own daylight window — sunrise to sunset, with half an hour added at the front for the dawn patrol and an hour at the back for the last of the glass. The window narrows through autumn and opens again in spring, on its own, because it’s reading the same sunrise and sunset the calendar is drawn from.

The other half is a logbook. Log what you actually found in the water and the app starts correcting the forecast for your break — the sandbar, the channel, the wind that bends around the headland. None of which a global weather model can see.

It’s free, there are no ads, and nothing is tracked. It came out of the gap Magicseaweed left when it shut down in 2023 — I wrote up the alternatives, honestly, including what mine can’t do.

Two projects, same obsession: a year of sun on paper, a day of it on a screen.