The PhenoPine is a Growing Degree Day (GDD) simulation model that can be used to trace the phenology of pine (Pinus roxburghii) under changing regimes of ambient temperature rise. The PhenoPine was developed using field-based observations for pine – a dominant tree species under the “Chir Pine forests” of Indian Western Himalayan region. Phenological stages of pine have been worked out on the basis of GDD. The GDD was computed assuming zero degree Celsius as base temperature and the accumulated averaged values over different phenological stages for developing phenology of the tree. The model has been built in Fortran Simulation Translator. Initially, the model has been developed to trace the impacts of temperature considering temperature as the major driving force for the phenology, while the lack of data for other forces also made this an obvious choice. Simulation through the PhenoPine can be done to trace the stages of initiation and termination of needle (leaf) formation, litter fall, cone formation; and the longevity of each phases under the changing regime of temperature rise.