Background <p>Rainfall intensity and timing may affect plant survival and growth differently across life stages. However, there is still a lack of studies that simultaneously examine these combined effects on plant performance, which largely limits our understanding of plant responses to climate change.</p> Methods <p>Here, we examined the impacts of rainfall intensity (−75%, −50%, 0%, +50%&#xa0;and +75%) and rainfall timing (early growing season: June–July; late growing season: August–September) on the survival and growth of seedling and juvenile <i>Poa crymophila</i> Keng, which is a dominant grass and serves as an important forage for livestock on the alpine rangelands of Qinghai-Tibetan Plateau.</p> Results <p>Rainfall intensity, timing, and plant life stage jointly affected the survival, growth, and biomass allocation of <i>P. crymophila</i>. Survival and growth increased with increasing rainfall, peaking under +50% rainfall for seedlings and under +75% rainfall for juveniles. Early-season rainfall promoted survival and growth far more than late-season rainfall, while early drought was more detrimental. Seedlings were more vulnerable to drought than juveniles but showed greater flexibility in biomass allocation.</p> Conclusions <p>Our study provides new insights into how rainfall timing and intensity interact with plant life stage to jointly affect plant survival and growth. Our results underscore the importance of management measures to mitigate the detrimental effects of early-season drought during the seedling stage.</p>