In the Algarve the coast turns ninety degrees and changes sea
At Cape St Vincent the coast makes a near right angle. To the south, a sheltered sea and water at around 21.7 degrees in August; to the west, open Atlantic and cold-water upwelling. In the air, about four degrees of difference.
The Algarve has a reputation for being one place, in the singular: golden beaches, honey-coloured cliffs and warm water. That description is accurate for one of its two coasts and useless for the other.
The difference is not a nuance. You can eat lunch in one and swim in the other on the same day, and find two different seas.
01 The corner of the continent
Cape St Vincent is the southwestern tip of the European continent, and there the coastline does something almost no other does: it turns ninety degrees. East of that point the shore runs west to east; north of it, south to north.
That turn completely changes each stretch's relationship with the prevailing wind and swell. The south coast has its back to the north-west, which is where the depressions and the ground swell come from; the west coast takes them head on.
From that comes everything else: air temperature, water temperature, the kind of beach, the vegetation and even where building happened and where it did not.
02 The wind that cools the water
The mechanism that makes the difference is called coastal upwelling and it works only on the western face. In summer the northerly wind dominates, blowing parallel to that coast and pushing surface water out to sea.
The gap is filled by water rising from below, which is far colder. The effect is large: several degrees below what you would expect, and capable of dropping the water temperature four or five degrees from one day to the next when the wind picks up.
The south coast does not have that regime. It faces the Gulf of Cádiz, sheltered from the north and with a wider shelf, so its water warms normally: at Faro it reaches around 21.7 degrees on average in August.
03 Four degrees of air and several of water
The difference is measured in the air just as clearly. The Faro station, on the south coast, records an average high of 29.2 degrees in August. Vila do Bispo, beside the western corner, stays at 25.1.
A methodological caveat is in order: the two series are not from the same period, 1991–2020 for the first and 1971–2000 for the second, so the contrast should be read as an order of magnitude and not an exact figure. Even so it is about four degrees, and it matches what you feel on the ground.
In winter the gap almost disappears: 12.3 degrees on average in January at Faro and 12.2 at Vila do Bispo. That is a revealing figure, because it means what separates the two coasts is neither latitude nor altitude, but a process that only operates in summer.
04 And north to south, three strips
To the east-west axis must be added another, perpendicular to it, that organises the interior. The Algarve divides north to south into three parallel strips, and the geology of each is different.
At the top is the serra, of schist and greywacke: poor, acidic, barely permeable ground, with the Monchique and Caldeirão ranges. The highest point is Fóia, at 902 metres, and from there everything descends.
In the middle is the barrocal, a band of limestone and dolomite where water sinks in and where springs, wells and dry-land crops appear: almond, fig and carob. It is the traditionally inhabited strip.
And below, the litoral: recent sediments, sand and the limestone and sandstone cliffs that give the south coast its postcard look. It is the narrowest strip and the one that now concentrates almost all activity.
05 The third coast, which is a lagoon
There is a third stretch that does not fit the description of cliffs and that covers the eastern half of the south coast. It is the Ria Formosa: some sixty kilometres of shallow lagoon separated from the sea by a chain of five barrier islands and two peninsulas, with around 18,400 protected hectares.
Its existence depends on the same orientation. On a coast sheltered from heavy swell, longshore drift can pile sand into bars parallel to the shore instead of taking it away. On the west coast, with the sea coming in, that does not happen.
And it is not a stable feature. The islands move: the bars migrate, the inlets open and close, and the whole chain shifts slowly eastwards. What you see today is not what was there a century ago.
06 How to travel it
The first practical consequence is that you choose a coast before you choose a town. If you want warm water and a calm sea, the south; if you want wind, waves and empty beaches, the west. They are different products and they are an hour apart by car.
The second is that the interior is not filler between the two. The barrocal and the serra have another climate, another agriculture and another settlement pattern, and ten kilometres from the beach the landscape already has nothing to do with it.
And the third reorders the trip: it pays to follow one cross-section, from the range to the sea, and then go to the cape. From the corner, with the Atlantic on one side and the gulf on the other, you understand at once why the two halves of the Algarve are not alike.
