Acta Scientiarum Polonorum

In the paper present state of the codification of soil freezing depths in Poland and their map is presented as
well as last proposals of their changes. Two of them are based on the use of so called air freezing index that
is a method of “degreedays” based on calculation of the number of days with minus air temperature. New
approach presented in the paper is based on the results of measurements of soil temperature carried out by
meteorological stations belonging to the Institute for Meteorology and Water Management – State Research
Institute. Annual (winter) maxima of the position of the zero centigrade temperature measured in the soil
were approximated by Gumbel probability distribution of extremes and characteristic values of 50 year return
period have been calculated. The soil conditions at the meteorological stations were taken into consideration
and correction coefficients have been proposed. Proposal of a new map of soil freezing depth in Poland is
presented for the soil assumed as a reference one.