Description: Mortality in general, and especially amongst the oldest old, is known to be partially shaped by seasons: winter is classically characterized by excess mortality. We therefore put forward the use of season-related life tables to study the mortality trajectories of the oldest old. This approach can be used to explore the plasticity of longevity, by opposing winter and summer trajectories. Furthermore, summerrelated life tables summarize the best conditions of mortality, i.e., the lowest values and the least fluctuating pattern. Results are presented for Switzerland, where season-related life tables have been computed until age 110.