Firefighters frequently have to work in direct solar radiant heat. To reduce firefighter heat stress, the influence of turnout garment properties on heat gain from solar radiation must be understood. This research studied the effects of color, texture, washing, and contamination of outer shell fabrics on heat loss through firefighter turnout fabric materials in simulated solar exposures. It showed that solar radiation could be a major factor in heat loss through turnout suits. Solar radiation equivalent to a sunny day completely reversed heat exchange through the turnout fabric systems, converting a heat loss of about 240 W/m2 to a heat gain exceeding 100 W/m2. Solar radiation caused turnout fabric systems to dry out and this decreased the performance of turnout systems that incorporated bi-component moisture barriers. Most significantly, the color of the outer shell had a major influence on lowering turnout heat loss in solar exposures. Composites with a black-dyed outer shell absorbed more solar energy than composites with lighter colored shell materials. Soot and fire-ground contaminants present on turnout outer shell fabrics also reduced heat loss under solar exposure. The findings of this study answered long-standing questions about the importance of turnout fabric color on heat exchange with the environment. The results provide additional motivation for efficient turnout cleaning practices, not only to reduce potentially toxic exposure to smoke contaminants, but to reduce turnout-gear-related heat strain on firefighters.