Temperatures measured directly on the ground may exceed air temperatures by 30 to 50 °C. A ground temperature of 84 °C (183.2 °F) has been recorded in Port Sudan, Sudan. A ground temperature of 93.9 °C (201 °F) was recorded in Furnace Creek, Death Valley, California, United States on 15 July 1972; this may be the highest natural ground surface temperature ever recorded. The theoretical maximum possible ground surface temperature has been estimated to be between 90 and 100 °C for dry, darkish soils of low thermal conductivity.