Ice Saints?

All this week the German press (mostly the weather) has been blathering on about 'Eisheiligen'  and today I finally remembered to look it up and see what they meant, I mean, I understood the vague principle* but not the precise translation and Leo offers the following '...according to popular belief a period in May with increased likelihood of night frost falling on the feast days of certain saints...'

* unexpected brass monkey weather during the night and early morning