Phenolic compounds and ascorbic acid are the main antioxidants in potato tubers. Synthesis of these metabolites is affected by biotic and abiotic factors. The aim was to understand how the genetic background, stage of tuber development and weather conditions impact the synthesis of phenolic compounds, ascorbic acid and tuber yield. Therefore, four potato cultivars with purple or yellow tuber flesh were grown at two different latitudes (61.2° N and 64.8° N) in two consecutive years in Finland. The potato tubers were harvested at different stages of tuber development. Purple-fleshed potato cultivars (‘Blue Congo’ and ‘Synkeä Sakari’) showed the highest gene expression levels for anthocyanin biosynthesis. The content of anthocyanins and phenolic acids in the tubers was the highest at around 70 days after planting (DAP) and decreased during tuber development. Temperature was the main weather variable affecting the synthesis of phenolic compounds. The potato trial located at 61.2 °N in 2014 (Kokemäki) was exposed to the highest temperatures and lowest precipitation. This produced tubers with reduced gene expression levels for the synthesis of phenolic compounds and the lowest content of anthocyanins, phenolic acids and ascorbic acid. All the potato tubers from this trial had scabs, which reduced the tuber quality.