The São Francisco River basin is one of the most drought-prone regions of Brazil. Seasonally dry tropical forests (SDTF) are widely distributed in the basin and we developed a short chronology of Cedrela fissilis annual ring widths from SDTF fragments based on 89 cores from 44 trees dating from 1961 to 2015. The average correlation among all radii (RBAR) is 0.52. The tree-ring chronology is correlated with wet season precipitation totals, must strongly and consistently near the beginning of the wet season. The spatial pattern of correlation covers most of the southern portion of the Brazilian Drought Polygon and the sub-basins of the two largest tributaries of the São Francisco River, in some areas exceeding r = 0.60. The chronology is also correlated with total annual discharge of the Rio São Francisco River measured at Barra (r = 0.489; 1961–2015), which is very promising in a country that generates two thirds of its electricity from hydroelectric power plants, particularly if this short chronology can be extended with trees exceeding 150-years old known to still exist in the region.