Beach Science · October 2026 · 3 min
A Beach in the Tropics Has Colder Water Than One in Portugal
La Mina sits 14 degrees from the equator. Its sea peaked at 18.9°C. We checked 47 beaches in three countries and the map of warm water is not the map in your head.
The rule everyone carries around is simple: closer to the equator, warmer sea. We have a year of sea temperatures for 47 beaches in Peru, Portugal and Greece. Three numbers from that table say the rule needs work.
18.9°C
That is the warmest the sea got in 2025 at La Mina, a pocket beach in Peru's Paracas reserve, at 13.9 degrees south. It is inside the tropics. Praia da Ilha de Tavira in the Algarve, at 37 degrees north, reached 22.5°C. The beach in Portugal beat the beach in the tropics by three and a half degrees.
The reason has a name. The Humboldt Current is a cold current that flows north along the west coast of South America, towards the equator, bringing cold water up from below as it goes. Off Peru it can hold the surface as low as 16°C at latitudes where most seas are above 25.
28.1°C
That is Punta Sal, also in Peru, four degrees from the equator, in March. Same country, same coast, nine degrees warmer than La Mina. In the far north the cold current meets warm tropical water, and the beaches there get the sea the brochure promised for the whole country.
Same country, same coast, nine degrees apart.
17.6°C
That is Praia da Adraga, near Sintra, in August, its warmest month. Across all 26 Portuguese beaches we hold, the August peak runs from 17.6 to 22.5°C. The Atlantic there photographs like the Caribbean and behaves like the Atlantic.
| Country | Beaches | Coolest peak | Warmest peak |
|---|---|---|---|
| Greece | 10 | 25.0°C, Platys Gialos, August | 27.4°C, Prasonisi, August |
| Portugal | 26 | 17.6°C, Adraga, August | 22.5°C, Ilha de Tavira, August |
| Peru | 11 | 18.9°C, La Mina, February | 28.1°C, Punta Sal, March |
Each beach's warmest month of 2025. Sea surface temperature from Open-Meteo Marine at the beach's coordinates. One year of data.
What it means for a trip
If warm water is the point, the dull answer wins: every one of the ten Greek beaches peaked between 25 and 27.4°C. If you are choosing a beach in Peru, the latitude matters more than the country. And if you are going to Portugal, go for the cliffs.
Which beach did you once walk into expecting a bath?