Beach
Heisaura
Tateyama, Japan · sea 26.1 °C at its warmest, in August

Sea temperature month by month
17.1Jan
16Feb
16.2Mar
17.2Apr
19.4May
21.6Jun
23.9Jul
26.1Aug
25.6Sep
23.6Oct
21.5Nov
19.1Dec
Monthly means in °C, NOAA OISST v2.1 climatology 1991–2020.
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 Heisaura?
The sea off Heisaura averages 26.1 °C at its warmest, in August, and 16 °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 Heisaura?
The sea reaches 20 °C or more from June to November. Twenty degrees is where most swimmers stop calling water cold; below it, a wetsuit helps.
Where is Heisaura?
Heisaura is on the coast of Tateyama, Japan, at 34.9431, 139.8131. The map on this site flies straight to it.