Olive groves are among the most endangered ecosystems in the Mediterranean due to climate change. Since 2018, the premature dropping of green olives (green drop) has been observed, leading to economic losses and a decline in olive production, though the real reason remains unknown. The study provides analysis of selected meteorological and phenological data for Olea europaea L. ‘Istrska Belica’ to evaluate the use of a chilling and forcing model for better understanding of flowering time dynamics under changing climate.The flowering process is affected by high diurnal temperature ranges (DTRs) in the period preceding flowering, resulting in earlier flowering. Despite annual fluctuations due to various climatic factors, an increase in DTRs has been observed in recent decades, but the mechanisms by which olive trees respond to high DTRs remain unclear. Chilling requirements are still well met in the region (1,500 ± 250 chilling units), but the total number of chilling units has decreased over the years. The growing degree hours (GDH) and the onset of flowering are strongly correlated. The results suggest that global warming is already affecting the synchrony between olive tree phenology and environmental conditions in the northern Mediterranean and may be the main reason for green drop. The trend towards earlier flowering and intermittent cold air intrusions during the spring months directly affect the flowering process, resulting in deformed flower buds and seedless fruit.