The period from May 11 to May 14 is known in folk meteorology as the Ice Saints, named after the feast days of four Catholic saints. These are the last days in spring when frost can still occur. However, frost days in May have become a rarity. And what does the future hold, are the Ice Saints still sacred?

Last Frost Falls Earlier

In a previous climate report we already wrote that the last frost day in spring has shifted forward by an average of about ten days over the past thirty to forty years. This is also evident in the image, where the black line for each year since 1901 indicates the last day on which the minimum temperature in De Bilt fell below freezing. The shift fits into the trend of increasing temperatures in the Netherlands. The last year with frost on or after the Ice Saints was 2020, the last year before that was 1973, almost fifty years earlier.