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The identification and delimitation of regions based on their agricultural aptitude is essential to assure the effective development and adaptation of climate-vulnerable regions, such as the Northeast Brazil (NEB). The objective of this study was to analyze the influence of the water balance on subsistence corn, bean and cassava yields during the period from 1990 to 2019. Thus, we used meteorological variables (precipitation, temperature, relative humidity and radiation) and water balance components (potential evapotranspiration, water stored in the soil, water deficit and surplus) in order to determine the best sowing periods for the aforementioned crops in the NEB. Data was assessed by using different statistical analysis such as Mann–Kendall's test for trend identification, analysis of variance and correlation heatmaps. Results showed an increasing trend for radiation, temperature, and potential evapotranspiration in the wetter regions of the NEB. An increase in water deficit conditions was also identified during September–October-November, and therefore a reduction in water stored in the soil during the following months in all regions of the NEB. In the wetter regions, potential evapotranspiration and temperature were positively correlated to bean and corn yields. In the drier regions, on the other hand, water stored in the soil and water surplus were more positively associated with yields. For the other climatic types, the following best sowing windows were identified based on the water balance: January through April (semiarid), March through June (dry subhumid), April through July (moist subhumid), March through July (humid B1) and January through June (humid B2). [ABSTRACT FROM AUTHOR]