You might have guessed: they are the "ice saints", usually between May 11 to May 13, but you can add "the cold Sophie" on May 15.
In Berlin the temperature accordingly changed from 27°C to 17 or even 14°C - my flowers on the balcony defiantly curl their lips (at least the Lamiaceae or Labiatae, haha) and try to look unimpressed.
Me too.
Though writing "cold Sophie" triggered a memory from decades ago: as a faithful wife I always followed husband to the different cities where he worked at the university (and that was not the best for my career) - but once I stubbornly refused to. In Trier - that was well-known throughout Germany - in my governing authority reigned a woman (whom I knew personally) called "Cold Sophie" - so with a stiff upperlip I stayed in Mainz (for a while, till we went to another city).