Plains rough fescue (Festuca hallii [Vasey] Piper) is an important, native forage grass species in Western Canada. Despite the high demand of seeds of this species, supply remains extremely limited mainly due to erratic seed production in native prairies. The underlining physiological and environmental principles remain largely unknown. Using historical weather records and long-term field observations, this study assessed the effects of summer, autumn, and spring temperatures and moisture conditions on seed production of Festuca hallii at two research stations in Saskatchewan, Canada. Our results showed that colder to normal temperatures and wet to normal moisture in summer and autumn favored flowering in the following year. Moreover, warmer to normal temperatures in the spring of the seed-producing year also promoted flowering while freezing events in spring negatively affected the reproductive success. Thus, irrigation in late summer and autumnmay be a valid strategy for stimulation of seed production in Festuca hallii. These findings can be useful to seed producers for commercial forage seed production. Moreover, conservationists could use this information to predict the likelihood that a particular year would be good for seed production.