The Ice Saints is the name given to St. Mamertus, St. Pancras, and St. Servatius in many European countries among others in Dutch, Hungarian, German, Austrian, Polish and Swiss folklore. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively. The period from May 12 to May 15 was noted to bring a brief spell of colder weather in many years, including the last nightly frosts of the spring, in the Northern Hemisphere.
This triptych I made last year, when I found some of my plants frozen in my garden after one of these cold nights... I warn all of you living in the Northern Hemisphere and who cares about their plants : keep eye on the weather forecast in the coming days!