Mamertus, the first of the Ice Saints

Mamertus is the first of five saints whose feast days have, over five centuries or so, coincided with a mid-spring cold spell often enough to warrant a foreboding nickname: the ice saints. His feast day and those of Sts.

The Ice Saints are St. Mamertus (or, in some countries, St. Boniface of Tarsus), St. Pancras, and St. Servatius. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively, known as the blackthorn winter in Austrian, Belgian, Croatian, Czech, Dutch, French, German, Hungarian, North-Italian, Polish, Slovak, Slovene and Swiss folklore.