Agriculture and food systems are highly exposed to sub-seasonal-to-seasonal climate variability as well as longer-run climate change. In recent decades these factors have contributed to faltering productivity in a number of regions; relatedly, progress against hunger in Africa, South Asia, and parts of Latin America and has stalled or even reversed. Many efforts have focused on increasing farm-level productivity, especially under hotter temperatures and more variable precipitation patterns. Less attention, however, has focused on the demand side. Here we use crop phenology observations, sub-seasonal and longer-run climate information, and farm output data to understand how markets and prices respond to growing season conditions; we then assess the implications of those relationships for food security both locally and more broadly. Analysis across scales reveals that climate-informed demand-side interventions would be especially beneficial for both low-income producers and consumers, and would help amplify the impact of supply-side breeding and management efforts.