The lowland hay meadows conservation status is increasingly at risk due to improper management and climate change, threatening plant communities, including Arrhenatherion alliance. As a result, species enrichment is required. However, natural plant self-establishment remains challenging due to the high variability in germination, largely caused by climate factors. Thus, a germination test is suggested before directly sowing local seeds in the field. Therefore, this study aimed to investigate how germination characteristics of five local species are affected by the interplay between species and weather factors, specifically mean temperature and total rainfall during seed filling and ripening. During warm, dry periods, the seed mass of Campanula patula L. and Centaurea jacea L. was higher (0.04 g and 1.87 g, respectively), whereas in wet periods, the seed mass of Achillea millefolium L. (0.10 g), Plantago lanceolata L. (1.24 g), and Tragopogon pratensis L. (7.41 g) was higher. The germination capacity was significantly affected by species-specific factors. Seeds of A. millefolium and T. pratensis during wetter years showed higher germination rates than other species, which exhibited the opposite trend. Additionally, a wetter collection period shortened t50 (time required for 50% germination) in all species except A. millefolium and T. pratensis, while C. patula remained unaffected in both years. A positive correlation was observed between seed mass, germination capacity, and speed, while a negative correlation with t50. Hence, an increase in seed mass leads to a reduced t50 duration. According to our findings, seed mass may serve as a reliable predictor of plant establishment in the field.