How climate change influences the dynamics of plant populations is not well understood, as few plant studies have measured responses of vital rates to climatic variables and modeled the impact on population growth. I used 25 years of demographic data to analyze how survival, growth, and fecundity respond to date of spring snow melt for a subalpine plant. Fecundity was estimated by seed production (over 15 years) and also divided into flower number, fruit set, seeds per fruit, and escape from seed predation. Despite no apparent effects on flower number, plants produced more seeds in years with later snowmelt. Survival and probability of flowering were reduced by early snow melt in the previous year. Based on demographic models, earlier snowmelt with warming is expected to lead to negative population growth, driven especially by changes in seedling establishment and seed production. These results provide a rare example of how climate change is expected to influence the dynamics of a plant population. They furthermore illustrate the potential for strong population impacts even in the absence of more commonly reported visual signs, such as earlier blooming or reduced floral display in early melting years. Survival, growth, and flowering in IpomopsisSurvival, growth, and flowering for individual Ipomopsis plants in the form of transitions between successive years in common gardens at two sites. See README file for details.Campbell_Ipomopsis_indivtransitions.csvAge-specific survival and fecundity for I. aggregataAge-specific survival and fecundity estimates for Ipomopsis aggregata in common garden at home site of I. aggregata. Please see README file for details.Campbellagestructured_I.aggsite.csv