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The genetic background determined the composition of black currants and the compositional response to weather conditions. The variety Melalahti had higher values for glucose and sugar/acid ratio and lower contents of fructose, citric acid, quinic acid, and vitamin C than the varieties Mortti and Ola (p < 0.05). In comparison to black currants grown in northern Finland (latitude 66°34′ N), the berries grown in southern Finland (latitude 60°23′ N) had higher contents of fructose, glucose, sucrose, and citric acid (by 8.8, 6.1, 10.0, and 11.7%, respectively) and lower contents of malic acid, quinic acid, and vitamin C (by 31.1, 23.9, and 12.6%) (p < 0.05). Fructose, glucose, and citric acid in Melalahti were not influenced by the weather, whereas their concentrations in Mortti and Ola correlated positively with the average temperature in February (Pearson’s correlation coefficients = 0.53−0.79, p < 0.01) and July (Pearson’s correlation coefficients = 0.63−0.87, p < 0.01) and negatively with the percentage of the days with a relative humidity of 10−30% from the start of the growth season until the day of harvest (Pearson’s correlation coefficients = from −0.47 to −0.76, p < 0.01). Positive correlations existed between fructose and glucose (Pearson’s correlation coefficients = 0.95−0.96, p < 0.01), citric acid and fructose (Pearson’s correlation coefficients = 0.57−0.75, p < 0.01), as well as between citric acid and glucose (Pearson’s correlation coefficients = 0.56−0.70, p < 0.01) in the three varieties because of the closely related metabolic pathways.