The introduction of non-native tree species has been used as a climate change mitigation tool. To ensure the anticipated benefits, the analysis of species radial growth reactions to meteorological factors should be carried out. Initially, tree species were introduced to non-native regions as food resources, yet the focus has now shifted towards favourable wood properties and growth rates. This study used tree ring width measurements of Japanese walnut Juglans ailantifolia and climate data to examine the relationships between these variables. A total of 30 trees were sampled from a stand located in the southern part of Latvia. Tree ring width (TRW) was measured, and residual chronology was derived. Pearson correlation analysis was used to detect the correlating meteorological factors, and a linear mixed-effects model was used to detect the key factors. The correlation analysis indicated generally low correlation coefficients between TRW and meteorological factors, primarily correlating with summer precipitation, both the current and preceding summer, highlighting carry-over effects. Furthermore, signature years underscored the negative effect of low temperatures and summer droughts on the radial growth of Japanese walnuts. However, the observed variation in TRW between years, not fully explained by meteorological factors, suggests a dynamic rather than stable relationship.