Beach
Plage des Nonnes
Meschers-sur-Gironde, France · sea 20.7 °C at its warmest, in August

Sea temperature month by month
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020, sampled 14 km offshore, at the nearest open water cell of a 0.25° grid.
About
beach in Meschers-sur-Gironde, France
Wikipedia has no article about this beach yet. It is on the atlas from its Wikidata record and its photograph.
Questions
How warm is the sea at Plage des Nonnes?
The sea off Plage des Nonnes averages 20.7 °C at its warmest, in August, and 9.9 °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 Plage des Nonnes?
The sea reaches 20 °C or more from July to August. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Plage des Nonnes?
Plage des Nonnes is on the coast of Meschers-sur-Gironde, France, at 45.5611, -0.9658. The map on this site flies straight to it.