Vol. 123, No. 3 * Pages 265–408 * July - September 2019

The purpose of the study was to determine the anomalous length of growing seasons, the frequency of their occurrence, and to determine the temporal and spatial changes of their frequency in Poland in the period 1966–2015. The analyses used daily average air temperature values for 30 stations located in Poland from years 1966–2015 (Fig. 1). The data was provided by the Institute of Meteorology and Water Management - National Research Institute. The growing season was defined as the period with average daily air temperature ≥5 °C. The start and end dates of the growing season were determined using the mathematical formulas proposed by R. Gumiński (1948). In the period 1966–2015 in Poland, anomalously short growing seasons occurred sporadically and covered the largest area of Poland in 1997. Short growing seasons were more frequent in the first three decades of the analyzed multi-year period, and long growing seasons were characterized by higher frequency in the second half of the surveyed period. Anomalously long growing seasons before 1990 occurred sporadically and only in individual stations. Anomalously short growing seasons occurred only in the middle eastern part of Poland, while anomalously long ones covered most of the country.