Potato is one the of world’s most important crops. It is grown primarily for human consumption but is also used to feed cattle and to produce alcohol and starch. In modern industry, potatoes are a major source of starch. Unpredictable growing conditions strongly influence the cultivation of starch potatoes. One of the best methods for dealing with unpredictable stresses, including those caused by climate change, is cultivation of stable and high yielding cultivars. In the present work, tuber yield and starch yield from a Polish post-registration series of field trials conducted in the years 2013–2016 were analyzed using three different linear mixed models, which can be associated with three different stability measures. It is shown that cultivar Pokusa was the highest yielding and the most stable cultivar in terms of tuber yield, while cultivar Kuras was the most stable and the highest starch yielding cultivar. Moreover, using mixed model factorial regression, it is shown that temperatures in June and August and total precipitation in August had significant influence on tuber yield in the analyzed series of field trials.