The current work was planned to study the effect of heat stress during the hot season on conception rate and estrus behavior of Baladi and crossbred cows. The cows were observed after month during the post-partum period. The cows divided into two groups, the first group treatment with spraying by water from one day at mating extended to seven days post-mating and the second group as control. The rectal temperature was recorded daily by digital thermometer onset day of mating till seven days post-mating. The present results demonstrated that mean rectal temperature at service  and during the next seven days after service were of Baladi and crossbred cows that sprayed by water was lower (38.75±0.15 and 38.77± 0.15^o C) than control group (39.18± 0.26 and 39.54± 0.24 ^o C) (P <0.05) respectively. The overall conception rate of Baladi cows was higher 42.5% compared to crossbred cows 35% during the hot months. Conception rate in Baladi and crossbred cows was higher in cows that sprayed by water (60 and 50%) than control group (25 and 20%) respectively. The occurrence rate (%) of heat signs (vaginal mucus discharge and mounting behavior) was more frequent in Baladi cows (45 and 50%) than crossbred cows (40 and 35%) respectively, but the difference was not significant (P <0.05). Concentrations of progesterone at estrus was higher (0.323±0.091 and 0.301±0.053 ng/ml) in pregnant than non-pregnant cows (0.247±0.042 and 0.211±0.031 ng/ml) in two breeds Baladi and crossbred cows (P <0.05) respectively. The present results clarified that treatment of the cows by spraying by water from the first day at mating till seven days post-mating lead to improve conception rate during the hot season. Therefore, this study recommends spraying water on cows before and after the mating period directly (body cooling) to improve fertility during the hot season under climatic conditions of Aswan Governorate.