This paper proposes an extended multi-segmented human bioheat model for high temperature environments considering the effects of high temperature on the metabolic rate and the cardiovascular system. This extended model is modified from an original model for normal temperature environments based on the energy balance equations from Salloum' model, and the human thermal regulation equations from Stolwijk and Fiala's work. The original model for normal temperature environments and the extended model for high temperature environments are validated with the existing experimental data. The results show that there are good agreements between the simulation results and the experimental data in both environments. Through the comparison of the simulated results with the original model and the extended model, it is shown that the original model would underestimate the skin and core temperatures, and underrate the impact on the human body from high temperature environments, e.g. underestimate the time to reach the utmost heat tolerance and skin burn. (C) 2014 Elsevier Ltd. All rights reserved.