The ice saints are a series of name days in mid-May that folk weather lore traditionally marks as the last risk of night frost. It is an old rule of thumb, not an exact forecast.
The days
The ice saints consist of the following name days:
- Mamertus (11 May)
- Pancras (12 May)
- Servatius (13 May)
- Boniface (14 May)
- Sophia, the “cold Sophie” (15 May)
Meaning for garden and construction
The rule of thumb is that frost-sensitive plants are only put outside after the ice saints, that is after mid-May. Frost-sensitive outdoor work is also traditionally planned around this. Think of certain concrete, plaster and masonry works, which can be damaged if it freezes before the material has hardened sufficiently.
How reliable is it?
Important to stress: the ice saints are folk wisdom, a rule of thumb and not a guarantee. Due to climate change, late night frost occurs less often than it used to. So use the ice saints as a broad point of attention when planning, but always base decisions on the current weather forecast and the requirements of the material.
Related terms
- Frost
- Frost line
- Frost boundary
- Frost resistance of concrete
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