Mean radiant temperature (MRT) is strongly influenced by ground radiation, which depends on both the ground view factor (Fg-p) and ground temperature (Tg). However, their roles are often oversimplified and rarely examined in detail. This chapter systematically evaluates the combined effects of Fg-p and Tg on MRT through field microclimate measurements in Shanghai and Monte Carlo ray-tracing simulations. The analysis shows that variations in human height (70–230 cm) exert negligible influence on MRT when the distance from the radiant ground boundary exceeds 40 m, and that differences in ground area become insignificant when this distance is no less than 70 m. Under uniform heating conditions, reductions in Tg are directly reflected in decreased MRT, while in non-uniform thermal environments, the extent of cooler surfaces substantially affects MRT estimation. Using averaged non-uniform Tg values may lead to overprediction of MRT by more than 2 °C. These findings highlight the importance of accurately incorporating both ground temperature and ground view factor into outdoor thermal comfort evaluations to avoid systematic errors and to improve the reliability of predictive models.