Outdoor workers are often subjected to thermal conditions beyond the comfort zone, but to what degree do such conditions affect the health and safety of those workers is still a matter requiring further investigation. The purpose of this study is to examine the relationship between thermal conditions and (1) heat-related disorders and (2) acute injuries using injury and illness data collected during the BP Deepwater Horizon clean-up operations. Over an eleven month period, 5,485 cases were identified as either heat-related or an acute injury (incident type) and further divided by severity. Daily weather data were used to estimate the wet bulb globe temperature (WBGT) based on the time of day. Heat Stress Levels intervals were defined using the estimated WBGT. Labor-hours by month were estimated by the prevailing shift length in the month and the number of workers. The incidents were assigned a Heat Stress Level and the number of labor-hours by heat stress level were determined. The next step was to calculate the incident rate ratio by Heat Stress Level against the baseline of thermal comfort. The results indicated that the rate ratios for heat-related disorders and acute injury increased for thermal conditions from 24⁰C-WBGT to 30⁰C-WBGT. There was a further significant increase in rate ratio for heat-related injury above 33 °C-WBGT. It was notable that the incident rates for both heat-related disorders and acute injuries increased at thermal conditions generally considered to be below the occupational exposure limit (OEL) at 30 ⁰C-WBGT. The rate of heat-related disorders increased substantially above the occupational exposure limit.