MAIZE (Zea mays L.) is the third-most significant cereal grain in Egypt, although it is susceptible to water stress, which results in substantial losses in both productivity and quality. A set of 100 S1-lines along with their top-crosses using two testers were evaluated under normal and water stress conditions. We used line × tester to evaluate general (GCA) and specific (SCA) combining ability effects for Days to 50% anthesis, Days to 50% silking, and Anthesis silking interval. Results of line × tester analysis showed highly significant differences among parents, crosses vs parents under normal and water stress condition. Both lines and testers showed significant and non-significant differences. Finally, line × tester analysis showed significant differences for Days to 50% anthesis and non-significant differences for Days to 50% silking under normal and water stress condition while, anthesis silking interval trait showed non-significant differences under normal condition and significant differences under water stress condition. Broad sense heritability values for the aforementioned traits were higher under water stress compared to those under normal condition. The high values of broad sense heritability make the selection process easier for the plant breeder and more accurate as the phenotype reflects its genotype. Our findings suggested that dominance genes predominately regulate the aforementioned traits. In conclusion, these S1-lines could be promising as a base for developing early- maturity and drought tolerant hybrids. This will help avoiding water stress events during growing season.