Golden sand
Arrietara
Spain · sea 21.7 °C at its warmest, in August

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020.
About
La playa de Arrietara o Arriatera (a veces considerada como dos playas distintas, Arrietara y Atxabiribil) se sitúa en el municipio vizcaíno de Sopela, País Vasco (España).
Questions
How warm is the sea at Arrietara?
The sea off Arrietara averages 21.7 °C at its warmest, in August, and 12.5 °C at its coolest. These are monthly means from NOAA's OISST v2.1 satellite and buoy record for 1991 to 2020, sampled at the beach's own coordinates.
When can you swim at Arrietara?
The sea reaches 20 °C or more from July to September. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Arrietara?
Arrietara is on the coast of Spain, at 43.3893, -2.9944. The map on this site flies straight to it.