Aims: In this study, six different table grape cultivars grafted on two drought-tolerant rootstocks in the province of Şanlıurfa, where has semi-arid climate characteristics, the effective heat summation (EHS) requirements were examined and the differences between both rootstocks and cultivars were tried to be determined.Methods and Results: Table grape varieties' (Red Globe, Trakya İlkeren, Ata Sarısı, Barış, Hatun Parmağı, and Horoz Karası), which grafted onto 1103 P and 110 R rootstocks, periodic phenological observations were made from the bud bursting to the harvest period in 2017-2018. The climatic data of these periods were also recorded. Using the Winkler index; the effective heat summation requirements of the examined cultivars were determined between the bud bursting-full blooming, bud bursting-veraison, bud bursting-harvest, full blooming-veraison, and veraison-harvest periods. After the harvest, the total soluble solids in the water content of the berries were determined. It was determined that the Trakya İlkeren cultivar was the cultivar with the lowest EHS requirement among the cultivars examined in all period intervals. The cultivar with the highest EHS requirement varied according to the examined period intervals. There was no statistically significant difference between the rootstock x variety interaction groups. The effects of rootstocks and the climatic characteristics of the years examined on the effective heat summation were found to be significant only between bud bursting and full flowering, whereas their effects on other phenological development periods were limited.Conclusions: It was determined that the main factor on the earliness of the grape cultivars was the genotype, in addition, the total effective heat required in the period between full bloom-veraison and veraison-harvest in the early-matured cultivars was lower than those in the mid-matured and the mid-late matured cultivars. It has been determined that the harvest dates of grape varieties can vary according to the years and these changes depend on the climatic characteristics of the region where the cultivation is made.Significance and Impact of the Study: It was determined that 1103 P rootstock can delay the time to reach different phenological development stages in grape varieties that grafted on it. If for any reason, it is desired that the grape varieties grown in a region reach the bud bursting, flowering, veraison, or harvest periods later, it is thought that grafting these varieties onto 1103 P rootstock will be beneficial.