Ectotherms from higher latitudes can generally perform over broader temperature ranges than tropical ectotherms. This pattern is thought to reflect trends in temperature variability: tropical ectotherms evolve to be ‘thermal specialists’ because their environment is thermally stable. However, the tropics are also hotter, and most physiological rates increase exponentially with temperature. Using a dataset spanning diverse ectotherms, we show that the temperature ranges marine and terrestrial ectotherms tolerate (the difference between lower and upper critical temperatures, and between optimum and upper critical temperatures) generally represents the same range of equivalent biological rates (e.g. metabolism) for cool and warm adapted species, and regardless of latitude. This suggests latitudinal trends in temperature variability may not be the ultimate mechanism underlying latitudinal trends in thermal tolerance. Rather, we propose that the reason tropical ectotherms can perform over a narrower range of temperatures than species from higher latitudes is because the tropics are hotter.