In this study, we assessed the Single Event Upset (SEU) rates of a LEO mission due to its passage in the South Atlantic Anomaly (SAA) during a geomagnetic storm. The South Atlantic Anomaly (SAA) represents a dangerous source of radiation for the LEO operations. Since the space weather continuously affects the inner magnetosphere condition, therefore, the inner radiation belt is subjected to significant variations, in particular during extreme space weather conditions. As the radiation environment depends essentially on the particle flux information, we have developed a numerical model to simulate the inner proton belt dynamics. In our previous work [Girgis et al. (2020b)], the short-Term variations of the inner proton belt was investigated according to the geomagnetic storm event of 15 May 2005 and the kinetic energy range for the implemented protons was from 70 to 180 MeV. The objective of this paper is to extend the previous work by assessing the corresponding SEU rates of the RAM devices mounted in a spacecraft operating in a circular orbit of 850 km, given the proton flux map information as the output results of the inner proton belt numerical model. It was concluded from the inner proton belt simulations during the geomagnetic storm, that the SAA proton flux was significantly enhanced, by > 10 % after the beginning of the storm and during the recovery storm phase. Consequently, the SEU rates were increased by 40 % during the recovery phase of the geomagnetic storm. The earlier and more accurate prediction of the SEU rates can save a LEO satellite mission from unexpected proton-induced single event upset rates during extreme space weather conditions such as geomagnetic storms.