The technological and polyphenolic parameters of grapes for juice processing obtained from successive harvests were studied in semi-arid tropical viticulture. Red grapes ?BRS Violeta? and ?Isabel Precoce? were harvested during the same year and analyzed based on a multivariate approach that included climatic variations. The grapes were marked by variations in flavonoid compounds, particularly anthocyanins. Temperature, global radiation, air velocity and evapotranspiration rates were associated with higher accumulation of bioactive polyphenols in grape berries and juices. The temperatures in February were associated with higher antioxidant activity in grape peels, while the highest thermal amplitude in August and November favored the accumulation of anthocyanins up to 564 mg kg−1. Flavanols and procyanidin compounds were more abundant in seeds when the maximum thermal amplitude was 13.8 °C. The climatic data together with the polyphenolic results point out useful information about appropriate periods for harvesting grapes with high phenolic content in tropical areas.