The intra-annual dynamics of wood formation were used to describe seasonal changes in xylem differentiation phases and to calculate the timing of cell development in Norway spruce (Picea abies (L.) Karst.). Tree-ring dynamics of Norway spruce from two altitudinal limits were studied to detect climate signals in the day-to-day dynamics of wood formation. The investigation was conducted during the years 2011–2012 in Trentino-South Tyrol (Eastern Italian Alps), in two sites Savignano (650 m a.s.l.) and Lavazè (1800 m a.s.l.). The climate is subalpine-continental type with a solstitial pluvial curve (maximum values in summer and minimum values in winter). Dendroclimatological analysis was performed to examine the relationship between the tree rings formation of Norway spruce and climatic parameters in the study sites. Climate–growth relationships were analyzed using correlation function (CF) analysis and moving CF (MCF), detecting correlations between wood formation and seasonal patterns of temperature and precipitation. During the monitored years, the effects of climatic variables on cell structure and stem diameter variation were examined daily. Cell structure was investigated through microscope analysis, and stem diameter variation was detected with microdendrometers. The results were interpreted according to dynamics of forest vegetation and synchronicity of cambial activity