Grain price (GP) volatility has been a central constituent of European commerce, with fluctuations in barley, rye and wheat prices having been carefully documented over centuries. However, a thorough understanding of the climatic and environmental drivers of long-term GP variations is still lacking. Here, we present a network of historical GP records from 19 cities in central and southern Europe for the 14th to 18th centuries. Spatial variability at interannual to multidecadal scales within this network was compared with reconstructed warm-season temperatures and hydro climatic conditions. We show that European GPs are tightly coupled with historical famines and that food shortages coincide with regional summer drought anomalies. Direct correlations between historical GP and reconstructed drought indices are low, hardly exceeding r = -0.2. Yet if the analysis is focused on extreme events, the climatic controls on high-frequency price variations become obvious: GPs were exceptionally high during dry periods and exceptionally low during wet periods. In addition, we find that GP variations were affected by temperature fluctuations at multidecadal timescales. The influence of summer temperatures is particularly strong over the 1650-1750 period, subsequent to the Thirty Years' War, reaching r = -0.40 at the European scale. This observation is supported by the lack of correlation among regional GP clusters during the period of hostilities and increased inter-regional correlation thereafter. These results demonstrate that the exchange of goods and spatial coherence of GP data in Europe were controlled both by socio-political and environmental factors, with environmental factors being more influential during peacetime.