foolish or extravagant behaviour, supposed to occur during the summer
midsummer madness in American English
noun
a temporary lapse into foolishness, senseless behavior, folly, etc., esp. during the summer
His plan to become a beachcomber is midsummer madness
Word origin
[1595–1605]This word is first recorded in the period 1595–1605. Other words that entered Englishat around the same time include: Creole, condensation, domain, redundant, slur