Climate shapes ecological communities across space and time. It sets physiological limits for organisms, driving population dynamics, species distributions, community assembly and ultimately, biodiversity patterns. Among the various aspects of climate, an underexplored dimension is its frequency distribution—how common or rare climatic conditions are across space. To uncover the mechanisms driving community-level responses to climatic frequency, we addressed three key questions: Does climatic frequency influence the phylogenetic structure of ecological communities across geographical scales? Are rare climates less suitable for supporting the diversity of closely related species than common climates? Do species with relatively recent ancestors exhibit similar preferences for climatic frequencies? We analyzed global data on climate, geographical distributions, and phylogenetic relationships of extant terrestrial tetrapods – amphibians, birds, mammals, and squamate reptiles. Globally, we found that ecological communities are less phylogenetically clustered in rare climates. Our results reveal that communities in rare climates exhibit lower phylogenetic clustering, reflecting greater phylogenetic diversity. Additionally, species co-occurring in both exceedingly rare and highly common climates tend to depart from their climatic optima. Our findings suggest that climate frequency plays a more influential role in recent ecological dynamics and evolutionary adaptations than deep ancestral constraints in shaping these communities.