Ten planting dates were selected at weekly intervals for the purpose of determining the optimum planting date for two late maturing sorghum (Sorghum bicolor) cultivars in the 1995 and 1996 cropping seasons. Both the floral characteristics and the ultimate grain yield were affected by variation in planting date. The highest grain yield for each cultivar (977 and 958 kg ha−1 for Janare and Farin Dawa respectively in 1995, and 975 and 955 kg ha−1 respectively in 1996) resulted from planting delayed for exactly 51 days after the onset of the rains. Consequently, 10–12 June appeared to be the optimum planting dates for sorghum in the area. A comparison of the result with previous work done in the same ecological unit revealed that delaying planting until 10–12 June increased grain yield by about 25–27 kg ha−1. The effects of the characteristics of the onset of the rains on the optimum planting date have been discussed and the implication of the study for traditional agricultural practice in Nigeria has also been noted.