Beach
Playa de Arenillas
Castro Urdiales, 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, sampled 15 km offshore, at the nearest open water cell of a 0.25° grid.
About
La playa de Arenillas está situada en el municipio de Castro-Urdiales (Cantabria, España).
Questions
How warm is the sea at Playa de Arenillas?
The sea off Playa de Arenillas 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 Playa de Arenillas?
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 Playa de Arenillas?
Playa de Arenillas is on the coast of Castro Urdiales, Spain, at 43.4040, -3.3123. The map on this site flies straight to it.