This paper presents a comprehensive steady-state numerical study for an occupant-loaded vehicle seat with internal heating under severe winter conditions. A participant-based postural study showed that the nominal peak occupant seat pressure was 6kPa on the seat cushion, and 2.5kPa on the backrest. Uni-axial compression tests also indicated non-linear stress-strain behaviors in seating. Using an internally developed 3-D numerical model, it was found that the thermal resistance from contact and clothing was uniform (hc=144W·K−1·m−2) throughout the occupied regions. Their contribution to the overall thermal resistance was relatively minor, however, compared to that of skin (hoverall=27.2W·K−1·m−2).The thermal-mechanical simulations were conducted at heat input levels between 20W and 80W, using I-DEAS 10 and the TMG package as the simulation platform. Comparisons was also made between occupied seat with deflected and non-deflected mesh. The occupant deflection helped reduce the thermal resistance in the occupied region, which resulted in a slight decrease in heater temperature, accompanied by an increase in the average surface temperature, compared to corresponding undeformed results.