Wörterbuch (en): Depth of frost penetration / Frost line
de:
Frosttiefe (f)
fr:
Profondeur de gel (f)
it:
Profondità di gelo
es:
Línea de congelamiento (f)
How far the frost has penetrated the underground. The frost penetration depth indicates the maximum value observed in a region. Soil temperatures near the surface are mainly determined by air temperature and climatic influences. So it is quite natural in Europe that in the winter season temperatures below freezing also occur in the soil. Permafrost can occur in regions with months of frost.