The research was performed to assess the direction, scope and significance of changes of thermal indices in agricultural seasons in the region of Bydgoszcz. Measurements of air temperature were carried out in a standard way, at the' Mo-chełek' Research Centre of the Faculty of Agriculture and Biotechnology UTP Bydgoszcz, located about 20 km from Bydgoszcz. The study included the normal period of years 1981-2010. The following agricultural seasons were taken into consideration: farming, growing, intensive plant growth, plant maturity and plant dormancy. The results of the research showed no significant trends among all
15 indicators characterizing the thermal agricultural seasons in the vicinity of
Bydgoszcz over the years 1981- 2010. In some cases (5 of the 15) was confirmed
a broadening of their temporal variability in the years 1996-2010, compared to the previous 15-year period 1981-1995. This may possibly be regarded as a symptom of the observed climate change. Long-term average values of the thermal indices in agricultural seasons examined during the period 1981-2010 were consistent with normative values for the region of Bydgoszcz quoted in publications, which characterize the Polish climate and agroclimate. It confirms the representativeness of the measurement point in Mochełek. The research confirmed a very high temporal instability of the thermal agricultural seasons in the region of Bydgoszcz which is characteristic for the moderate and transitory climate in Poland.