Heat stress reduces marketable tuber yield and quality of potatoes. Tuber defects can be external (heat sprouts, chained tubers, shape deformations) or internal (vascular discoloration, internal heat necrosis). Successful cultivation of potatoes under heat stress requires planting heat tolerant varieties that can produce high yields of marketable tubers. Field trials were conducted near Springlake, Texas (heat stress location) for two years. Two planting dates per year were used to identify the most stressful planting time. Ten potato clones (six TAMU released varieties and two top commercial varieties for processing: Russet Burbank (frozen French fries) and Atlantic (chipper)) were tested. Yield and quality parameters did not differ in response to planting dates. However, the 10 potato clones differed for reaction to heat stress based on marketable tuber yield, average tuber weight, and percent tubers affected with defects. Russet Burbank showed a high percent (58%) of tubers with external defects. Atlantic showed the highest percentage (52.5%) of internal defects (mainly internal heat necrosis). Vanguard Russet had the highest marketable yield (15 Mg/Ha), average tuber weight (129 g) and low percentage of external and internal defects. For future heat stress tolerance studies, Russet Burbank and Atlantic can be used as heat susceptible controls for external and internal tuber defects, respectively, whereas Vanguard Russet can be used as a reliable heat tolerant control. Including appropriate controls in screening new potato clones develop by the TAMU potato breeding program will aid in future heat stress studies and help identify those clones that have superior heat tolerance.