The seasonal cycle of temperatures on Pangaea (early Late Permian configuration) is simulated with a two-dimensional energy-balance climate model. Results indicate that the annual range of temperatures in the Southern Hemisphere of Pangaea was considerably larger than any occurring at present. Maximum mean monthly summer temperatures are 38 °C; daytime highs probably exceed 45 °C in some regions. However, summer temperatures in polar regions are considerably lower (0-5 °C) and are favorable for persistence of ice in eastern Australia and glaciation in Siberia—conditions that receive some support from geologic data. These simulations suggest that very high summer temperatures and a large annual range are major features of supercontinent environments. Such conditions may have significantly influenced the distribution of terrestrial Permian biota. Our results are difficult to reconcile with postulated "equable" climates for some supercontinent configurations.