Climate change is predicted to increase the severity and frequency of environmental disturbances, including storms, floods, and droughts. While they are often short lived, these disturbances act as strong selective agents. Hence, while evolution during an extreme event may be adaptive, the resulting phenotypic changes may become maladaptive when the event ends. Using individual-based models and analytic approximations that fuse quantitative genetics and demography, we explore how heritability and phenotypic variance affect population size and extinction risk in finite populations under an extreme event of fixed duration and under repeated extreme events. Because evolution results in greater maladaptation and slower population recovery following an extreme event, greater heritability can increase extinction risk an extreme event lasts a single generation or less. Alternatively, when an extreme event is sufficiently long, heritability often helps a population persist. We also find that when events are repeated, evolution is harmful unless the events are autocorrelated in time.