Characteristic of bioclimatic conditions in Poland based on Physiologically Equivalent Temperature

The aim of the study was to characterise bioclimatic conditions in Poland in the times of progressing warming. This type of research permits the verification whether the progressing climate warming also translates into a change in bioclimatic conditions. This study was based on data obtained for the period 1966-2021 from 37 synoptic stations located in Poland. All the data series were uniform and obtained from the data base of the Institute of Meteorology and Water Management-National Research Institute (IMGW-PIB). The study revealed high variability of bioclimatic conditions in Poland both in spatial and in temporal terms. The lowest mean annual PET values were recorded in the north and north-east of the country and the highest in the south-west of Poland. The study revealed changes in the frequency of occurrence of days with cold and heat stress, as well as days with no thermal stress. The most intensive changes were determined for days with cold stress. A decrease in the number of days in this category translated into an increase in the number of days with no thermal stress and days with heat stress.