midsummer (n.)

"the middle of summer, the period of the summer solstice," Old English midsumor, from mid (adj.) + sumor "summer" (see summer (n.1)). Midsummer Day, an English quarter-day, was June 24 (Feast of the Nativity of St. John the Baptist). Astronomically, midsummer falls on June 21, but the event traditionally was reckoned in northern Europe on the night of June 23-24 (with summer beginning at the start of May). Midsummer night was an occasion of superstitious practices and wild festivities.