Wieloletnia zmienność okresu bezprzymrozkowego w Polsce w latach 1951–2006

In the study tendencies in changes of frost-free season at 20 meteorological stations in Poland in the period 1951-2006 were examined. Both changes in the beginning and the end of frost-free season and its length were analysed. At 13 of those examined stations the frost-free season were beginning sooner and sooner (16 days/50 years an average), whereas the tendencies in changes of the end of analysed season lack such a clear distinction. Nevertheless, the length of frost-free season was noticed to be longer from about 15 days in Legnica to about 32 in Łódź. The most significant of the described changes occurred in the west part of the country and the lowest in the east part.