The current study aimed at assessing the heat tolerance of twelve wheatgenotypes under six environmental conditions (two locations and three years). Wheat genotypes were sown in two locations (Sohag and Assiut, Egypt) at two dates: November (favorable) and December (heat stress) during winter seasons of 2005/2006, 2006/2007 and 2007/2008. The combined analysis of variance showed that the flag leaf area, days to heading, plant height, spike length, 1000-kernel weight, biomass and grain yield were significantly influenced by years, locations, sowing dates, nitrogen fertilizer levels and genotypes. The results showed that sowing at the favorable date using 100 kg/fed Nitrogen fertilizer increased all studied traits. The stability analysis revealed that four and three genotypes were high and intermediate yielding and stable for yield, respectively. The temperatures were decreased up to 2.50 to 6.39°C at sowing late date than at the favorable sowing date. However among wheat genotypes a wide variation was found in response to heat tolerance. The results indicated that the 1000-kernel weight and grain yield traits are stable under heat stress. Some wheat genotypes conferred productive and adaptive advantages where they expressed high yield and yield stability when compared to other genotypes. This study indicated that higher 1000-kernel weight and days to heading are the two important traits which could be considered as potential selection criteria for yield under heat stress.