Serving temperatures of Sake (download) by Philip Harper (Master Brewer).
If it’s light, fruity, fragrant and fresh, serve it cold.
If it’s funky, ricey, earthy or old, drink it at room temperature or above.
– Hot sake: kanzake (o-kan) 燗酒、お燗.
Hitohada (body temperature) →　Nurukan (literally, lukewarm, about 40℃) → atsu-kan (“hot” kan, about 50℃).
– Room Temperature （Jô-on, 常温）. Sake served at room temperature is confusingly called hiya, written with a character (冷)meaning cold.
Which sake should be served warm, and which cold?
– The big myth: Good Sake Cold, Bad Sake Hot.
The mechanics of taste and temperature.
As temperature rises, sweetness and umami elements become more prominent, bitter and astringent flavours less noticeable. Acidity itself is unaffected, though the shift in other flavours can make it seem more prominent to some. As might be guessed from these trends, very sweet or low-acidity sake is often served cold, and sake with strong astringency frequently benefits from warming – may, in fact, have been brewed with that intention.
Unpasteurized (nama) sake, fragrant styles (especially dai-ginjo, but also honjozo or other styles with strong fruity or floral aromatics), low-alcohol sake, .
High acidity sakes (many junmai (“pure rice”) sakes, kimoto/yamahai), not-so-flowery ginjo and honjozo, many “regular” products.