A study was conducted during two growing seasons in Sudan to test the effect of temperature during different phenological stages on yield, yield components, and yield stability of wheat cultivars. Five cultivars were sown in early November, late November and mid-December on heavy clay, Vertisols. Duration of phenological stages was affected by cultivars and sowing dates. Total thermal units for the full cycle of these wheats was 2390 (°C day). Grain weight was negatively correlated with mean air temperature during grain filling (r= -0.83 * * ) with an increase of 1°C causing a decrease of 4 mg in grain weight. It seems that the best plan for such a hot environment is to sow late-maturing cultivars early in the season, and to sow early-maturing cultivars late, so that ear emergence coincides with the coolest period. The cultivar environment interaction was significant for grains/ear, grain weight and yield. The cultivar El Neilein was consistently high yielding and more stable, by several indices, across environments.