noun
everlasting summer; eternal summer
Poetic or literary noun for a place or state where summer never ends; often used in travel writing, song lyrics, and figurative descriptions of tropical locales.
南の島はまさに常夏の楽園だ。
The southern island is truly a paradise of everlasting summer.
彼女は常夏の国に移住したいと言っている。
She says she wants to move to a country of eternal summer.
真夏 means 'midsummer' or 'the height of summer' within a seasonal cycle, while 常夏 describes a perpetual summer-like state.
Compound of 常 (とこ, 'everlasting') and 夏 (なつ, 'summer'). The reading とこ is an older combining form meaning 'eternal' or 'unchanging'.