Three environmental conditions were applied to study the effects of climate on the thermal comfort of flame resistant fabrics. Standard, cool and dry, and hot and humid conditions were used. The clo value and permeability index were also investigated to predict thermal comfort. The clo rating of test fabrics remained unchanged with climate changes in the surrounding environment. Permeability index value changed according to environmental conditions, and it increased from cool and dry conditions to hot and humid conditions. The thermal comfort zones changed with changes in the environmental conditions. Projected comfort limits were calculated for two other environmental conditions based on the data measured at the standard condition. They were also compared with measured comfort limits obtained for those conditions.