Climate has an important impact on grape and wine qualitative parameters. Experiments in controlled conditions have shown that the major climatic factors affecting polyphenol accumulation are radiative and thermal conditions; in particular, high temperatures inhibit anthocyanin formation and modify the composition of the anthocyanin fraction. The aim of this study was to compare climatic data and berry composition throughout a ten-year period, in order to explore the relationships between phenolic compounds concentration in 'Nebbiolo' grapes and climatic trends. Phenolic compounds concentration was monitored during the 2000-2009 period at four vineyard sites in Piedmont. Meteorological data were collected in the study areas and bioclimatic indexes were calculated. A qualitative and climatic dataset was created and correlation analysis was carried out. The results show that bioclimatic indexes linked to temperature have the highest impact on anthocyanin and flavonoid concentration, while little effects of global light radiation and of rainfall were observed.