The experiment with different seeding date was conducted at the hybrid rice seed production site in Yancheng City to explore the impact of weather conditions at the heading stage on seed setting rates for female parents. Exposed to consecutive high temperature lasting for 11 days in the mid-to-end of August 2013, in Yancheng, before blooming, seed setting rate of the female parent in 2013 was significantly reduced by 6.89 percent on average compared with that in 2011. Meanwhile there has been great differences in high-temperature sensitivity among various combinations, with Xinliangyouxiang 4 and Xinliangyou 223-gai being more insensitive than Xinliangyou 223. The out-crossing rates of all the female parents showed a significant negative correlation with high temperature in 2013, but no correlation in 2011 in comparison. Regression analysis showed that when the 10 d average temperature before and after heading stage increased up to 28.0℃, the out-crossing rate of the female parents began to fall, and when it came to 29.0℃ the out-crossing rate significantly reduced.