Abstract The influence of climate on winter wheat yields were examined in two important global breadbaskets—the Picardy Region of northern France and the Rostov Oblast of southern Russia. Thirty-year climatologies were established for each region and the magnitude of change between 1973 and 2010 was quantified for a variety of climate variables important to crop development. Using a “first differences” analysis, the aspects of climate that winter wheat yields have been most sensitive to were identified and the impact of changes in these variables on winter wheat yield trends was quantified. A number of aspects of climate have changed at unprecedented rates in the two regions. Between 1973 and 2010, summer precipitation totals decreased by 61% and maximum summer temperatures increased by 4 °C in Rostov, while fall precipitation totals decreased by 9% and maximum spring temperatures increased by 2.4 °C in Picardy. In addition, winter wheat yields were strongly correlated with a number of climate variables, although the most important drivers of yield variability differed between the two regions. May and June average temperatures explained 49% (p