The objective of the work was to evaluate the effect of hydrothermal conditions on oats yields produced in east-central Poland. Hydrothermal conditions were determined based on the Sielianinov’s hydrothermal coefficient for nine IMGW (Institute of Meteorology and Water Management) stations located in the study area. The second data set consisted of oats yields compiled and published by the Main Statistical Office. Average yields as well as minimum and maximum yields were analysed. The relationship between oats yields and hydrothermal conditions was examined using a step-wise linear regression model. Correlation coefficients were negative in April and positive in June at all the stations. The relationships were confirmed by an analysis of regression equations. The regression equations also included coefficients for May and June which, however, were not statistically significant. Yield variation, described by regression equations of the dependence of oats yield on Sielianinov’s hydrothermal coefficient value was accounted for from 19 (Siedlce, Biała Podlaska) to 50% (Ostrołeka).