Based on the intensive observations of temperature and development course during grain filling period, weight per 1000 seeds, and grain filling rate of double harvest paddy rice at different agrometeorological stations from three southern provinces of China, it was founded out that average temperatures during the reproductive growth periods of doubleharvest early paddy rice, doubleharvest late paddy rice, and singleharvest paddy rice increased by 2 ℃ in recent years. The decrease in the duration of headingmilk of early and late paddy rice was about 6 days and the duration of headingmature decreased by about 6 days for early paddy rice and 5 days for late paddy rice. Climate warming usually happened with water stress. The number of the days for grain filling was significantly negatively correlated with average temperature and positively correlated with average relative humidity, identified by regression analysis. Climate warming resulted in the decrease in the sampling numbers of weight per 1000 seeds and grain filling rate taken from the Monitoring Regulation of Agrometeorology currently used. These measurements can only indicate the status of rice at the late stage of grain filling. The results also indicated that climatic warming has caused the earlier development and shorter duration of grain filling of rice in the south of the Yangtze River. The Monitoring Regulation of Agrometeorology has to be modified. The first time for measuring the weight of per 1000 seeds and grain filling rate should be shifted to the day of universal heading or 5 days after universal heading. Thus, the observation should be taken every 5 days to enhance the applicability of the measured data and the availability of service.