Frequent winter injury is a major problem in apple (Malus domestica Borkh.) production in northern areas. Discriminant and cluster analysis were used to determine the critical climatic factors associated with winter injury occurrences in south-western Finland over a 71-yr period, 1927 to 1998. Years with and without winter injury were best characterized by variables indicating mid-winter severity: the monthly mean, minimum, and maximum temperatures from January to March. Also, weather conditions during the preceding summer and fall contributed significantly to the discrimination between winter injury and no injury years. A decrease in growing degree days, drought in August, and a high level of precipitation in September were associated with winter-kill years, probably due to their impact on the annual cycle of vegetative growth. The hypothesis on the adverse effect of mild spells during early and mid-winter could not be verified by this study. Mid-winter frost resistance was confirmed as the most important winter hardiness characteristic in the semi-maritime climate of Finland. At high latitudes rootstocks and cultural practices should be chosen to ensure that trees acquire vegetative maturity even under adverse weather conditions. Key words: Malus domestica Borkh., winter injury, climate, variety, discriminant analysis, medoid clustering