Exposure to high-altitude and cold environments can easily induce cold injuries. Notably, outdoor workers exhibit a greater cold exposure risk. Herein, an extended multi-segmented human bioheat model was developed considering the characteristics of physiological responses in high-altitude environments. The model accounts for the effects of atmospheric pressure changes on metabolism, and the convective and evaporative heat transfer coefficients were adjusted. The model predictions suitably agreed with the experimental data at altitudes of 2560 m (74.11 kPa) and 4290 m (59.35 kPa) and an ambient temperature of −10 °C. The maximum mean square errors (MSEs) of the predicted mean skin temperatures of the hands, face, forehead, thighs, and feet were 1.02 °C, 0.52 °C, 0.41 °C, 0.35 °C and 0.47 °C, respectively. The improved model, combined with wind chill temperature (WCT) and frostbite standards, was applied to analyze the cold exposure risk of outdoor workers in different regions of China. Over the past decade, the average WCT in January ranged from −43.98 °C to 21.04 °C, with an average of −14.06 °C. Cold exposure risk analysis for outdoor workers in Heilongjiang Province in January 2023 revealed that after 30 min, the predicted skin temperature of the hands across different regions ranged from 5 °C to 10 °C, with finger temperatures mostly below 5 °C. Heigang city exhibited the highest risk, with predicted skin temperatures below −0.25 °C, indicating frostbite risk. The integration of the proposed model with cold risk analysis contributes to precise evaluation of the cold exposure risks of outdoor workers in severely cold regions.