Abstract Irrigation is important for food security, however, water requirements for sustainable irrigation may be affected by climate change. The study analysed water requirements of two commonly cultivated crops in the dry season in the Ghanaian Savannah regions under baseline and future periods. Crop water requirement (CWR) and crop irrigation requirement (CIR) were lowest in baseline periods and increased in the 2020s, 2050s, and 2080s for RCP 4.5 and RCP 8.5 at all locations. CIR was higher for tomato as compared to onions for most locations. Seasonal changes in the CWR ranged from 2–9, 3–12, and 3–12% and 2–8 3–12% and 5–18% for the 2020s, 2050s and 2080s under RCP 4.5 and RCP 8.5, respectively, for both the crops. Bole and Zuarungu recorded highest increases in CWR for tomato, whereas the least change was observed at Yendi for onions. Changes in seasonal CIR ranged from 3–19, 2–21, and 6–22%, respectively, for the 2020s, 2050s and 2080s for RCP 4.5. Under RCP 8.5, changes in seasonal CIR ranged from 3–23, 5–23, and 6–27% were observed for the 2020s, 2050s, and 2080s, respectively. Highest increases in CIR were noticed at Bole and Zuarungu for tomato, whereas the least change was observed at Wenchi for onions. Findings of the study support zero hunger and climate action, goals 2 and 13 of the Sustainable Development Goals (SDGs). HIGHLIGHTS The study analysed water requirements of two commonly cultivated crops in the dry season in the Savannah regions of Ghana. Crop and irrigation water requirements were generally lowest in baseline periods and increased in the 2020s, 2050s, and 2080s under RCP 4.5 and RCP 8.5. Highest increases in irrigation requirement were noticed at Bole and Zuarungu for tomato, whereas the least change was observed at Wenchi for onions.