Medical practitioners and international labor organizations have long voiced the detrimental impacts of extreme heat and humidity on workers? health and productivity. Excessive nighttime temperatures following hot days do not allow for a person to recover and compounds health impacts. Yet, awareness of heat stress and capacity to take adaptive measures remains low among employers and employees, with low-income migrants or outdoor laborers like farmers, street vendors or construction workers in tropical climates at particular risk. We investigate trends in the apparent temperature heat index for Da Nang, Vietnam, and project how it might change by 2050 using an ensemble of statistically downscaled climate change scenarios. Daytime heat index values breach the 34�C indoor work safety threshold set by the Vietnam Ministry of Health nearly year-round by 2050; the lower, outdoor work thresholds are constantly exceeded; and, nighttime values average 29.5�C during the months of June to August. The situation facing many workers in Da Nang is similar to that of workers in tropical climates throughout Asia. Many are poor and unable to afford air conditioning, have little labor recourse with employers, or if self-employed, are afraid to take time off during the heat of the day because of lost revenue. Without better health and labor policy enforcement, awareness raising activities, better heat warning systems and support for adaptive measures, climate change impacts on heat stress and labor productivity will be highly negative. Keywords: Climate Modeling and Scenario Planning; Extreme Heat; Health; Social Vulnerability