a temporary lapse into foolishness, senseless behavior, folly, etc., especially during the summer: His plan to become a beachcomber is midsummer madness.
Origin of midsummer madness
First recorded in 1595–1605
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for midsummer madness
And we were reminded too of the Midsummer-madness that overtook the company in Dear Brutus.
British Dictionary definitions for midsummer madness
foolish or extravagant behaviour, supposed to occur during the summer
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012