The study investigates the impact of rising summer temperatures on the masting behavior of European beech (*Fagus sylvatica*). Masting, a phenomenon where trees produce seeds synchronously in response to environmental cues, is crucial for pollination and seed predation dynamics. The research analyzed 50 long-term datasets of seed production across the distribution range of European beech and found that increasing summer temperatures (June-July) significantly reduced the interannual variability and synchrony of seed production. This "masting breakdown" was more pronounced in populations experiencing rapid temperature increases. The study also observed that larger increases in summer temperatures were associated with greater decreases in the coefficient of variation of population-level seed production (CVP). Additionally, the frequency of high-seeding years increased, while low-seeding years became less frequent. These changes in masting patterns could reduce the viability of seed crops and alter forest ecosystem dynamics, particularly in terms of seed predation and pollination efficiency. The findings highlight the need for further research to understand the broader ecological consequences of masting breakdown and to monitor reproductive patterns in beech forests.The study investigates the impact of rising summer temperatures on the masting behavior of European beech (*Fagus sylvatica*). Masting, a phenomenon where trees produce seeds synchronously in response to environmental cues, is crucial for pollination and seed predation dynamics. The research analyzed 50 long-term datasets of seed production across the distribution range of European beech and found that increasing summer temperatures (June-July) significantly reduced the interannual variability and synchrony of seed production. This "masting breakdown" was more pronounced in populations experiencing rapid temperature increases. The study also observed that larger increases in summer temperatures were associated with greater decreases in the coefficient of variation of population-level seed production (CVP). Additionally, the frequency of high-seeding years increased, while low-seeding years became less frequent. These changes in masting patterns could reduce the viability of seed crops and alter forest ecosystem dynamics, particularly in terms of seed predation and pollination efficiency. The findings highlight the need for further research to understand the broader ecological consequences of masting breakdown and to monitor reproductive patterns in beech forests.