A hydrocooling system applied to Semillon (Vitis vinifera L.) grapevines as a means of protecting the vines from recurrent high temperatures. This system was assessed for impacts on vegetative and reproductive growth and development as well as for carbon economy of vines growing in vineyard conditions. The system maintained canopy temperatures at 35°C over the growing season. Leaf and bunch biomass and yield were all higher in the hydrocooled compared with control vines: the major effect was on dynamics of leaf and berry expansion. Leaf expansion was delayed and occurred over a longer duration whereas berry expansion was advanced and occurred over a longer duration than in control vines. Berry ripening was also faster in the hydrocooled vines and berries had accumulated more sugar at harvest. Leaf photosynthesis along the shoot was also higher in hydrocooled than control vines and there was a significant effect of leaf position on rates of photosynthesis of the hydrocooled vines but not with control vines. However, no differences were observed in the net shoot carbon budget. Lowered canopy temperatures were beneficial for yield and berry composition and, therefore, the cooling system warrants adoption in vineyards at risk from high temperature events during the growing season.