The aim of the work was to determine a potential decrease in yields and a risk of cultivation of field cucumber of pickling varieties in Poland caused by the delay of the dates: flowering, fruit setting and harvesting. In order to carry out this task the following phenological dates from whole Poland were used: emergence, flowering and fruit setting and also the agrotechnical dates: sowing and harvesting from 28 experimental stations of the Research Centre for Cultivar Testing (COBORU) through 1966–2005. On the basis of linear regression analysis the relation between the yield of field cucumber and the analysed agrotechnical and phenological dates was determined, taking into account the trend of the yield from 1966–2005. Moreover, a potential decrease in the yield caused by the delay of phenophases was calculated for both the whole country and for its particular regions. The measure of matching of the regression function to empirical data was the determination coefficient and the regression equation error. Moreover, to determine the share of each of the selected factors in the prediction of cucumber yield partial correlation analysis was used. The obtained results may be used, among other things, in the meteorological protection of agriculture and improvement of new technologies of cucumber field cultivation.