To predict the blooming date of ``Yumyeong`` peach trees, the models for flower bud developmental rate (DVR) were constructed. The DVRs were calculated from the demanded times at controlled air temperatures. The branches of ``Yumyeong`` peach trees were incubated at three different temperatures of 9.7, 15.2, and 18.9oC. The DVRs were also constructed with blooming dates and air temperatures in the field, collected from 1979 to 2008 at the experimental orchard of National Institute of Horticultural and Herbal Science, Suwon, Korea. All the DVRs increased linearly or exponentially with air temperature. The DVR equations evaluated under controlled air temperatures were y=0.0018x+0.0051 and y=0.0125e0.0603x. The DVR equations under field conditions were calculated as y=0.0039x-0.0112 and y=0.0062e0.1512x. These DVR equations offer developmental indices and predict the date for blooming with air temperature data. These DVR equations were validated against the blooming data observed in the field. When the blooming dates were calculated with exponential DVR equations and daily air temperature data, the root mean squared errors between the observed and predicted dates were around 2 days. These results suggest that the DVR models are useful to predict the blooming date of ``Yumyeong`` peach trees.