Global studies of organismal distribution and climatic vulnerability rely on the mostly untested assumption that heat tolerance restricts the maximum temperatures estimated at the warm edges of their geographic distribution (Tmax). Herein we test this assumption across the animal kingdom and examine whether the strength of restrictions depends on how challenging heat becomes for their tolerance. Thermal limits restrict species’ warm distributional edges across the animal kingdom, being restrictions less consistent for reptiles and describing a striking non-linear relationship for marine fish that contrast with terrestrial groups. Besides, heat tolerance restricts the geographic warm edges more strongly for species exposed to more defying temperatures at ranges’ warm edges.