The actual observation photos of Yali pear flower bud development from 2012 to 2018 are used to accurately determine the occurrence time of each node of Yali pear flower bud development phenological period. Based on this data, the meteorological factors in each phenological phase in Yali pear bud development are studied. The effects of meteorological influencing factors on flower bud development are analyzed according to the phenological phases. The result shows that the temperature plays a leading role in the development of the flower buds of Yali pear, and three prediction indexes, i.e., the average daily temperature, ≥0 °C active accumulated temperature, and ≥3 °C effective accumulation temperature in the periods from germination to first flowering, sprouting to first flowering, squaring to first flowering, are selected to determine the Yali pear flowering dates. According to the application test from 2016 to 2018, the prediction error between the predicted results and the actual flowering of Yali pear is within 1 to 2 days when the prediction time is 10 to 12 days, and the predicted results are completely consistent with the actual flowering of Yali pear when the prediction time is 7 days. This study overcomes the shortcomings of traditional plant flowering forecasting, such as the lack of phenological data before flowering and the inability of the preflowering period analysis, and introduces the medium and longterm weather forecasting products into flowering forecasting, which provides a new idea for flowering forecasting.