noun
Formal or literary term for the heat that remains after summer has officially ended, similar to 残暑 but more poetic.
See also: 残暑
九月に入っても残炎が厳しい。
Even in September, the lingering summer heat is severe.
noun
remaining flame; dying embers
Formal or literary term for a flame that still burns after a fire has mostly gone out, or metaphorically for something that persists.
暖炉には残炎がまだ揺らめいていた。
The remaining flames were still flickering in the fireplace.
残暑 is the common word for lingering summer heat; 残炎 is a more literary and less frequent synonym.
Compound of 残 (remaining) and 炎 (flame, heat). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for describing lingering natural phenomena.