Extreme temperature significantly affects workforce health during the summer in locations with sustained high temperatures. The exposure of workers to excessive heat has increased in the last decades, and it is correlated with reduced productivity and work efficiency. The effects of extreme heat on the health of outdoor workers in the southwestern USA were assessed using the heat index (HI) calculated using temperature and humidity information from National Oceanic and Atmospheric Administration and data on occupational injuries/illnesses from the US Bureau of Labor Statistics. The analysis of the data was performed using the Spearman's rho nonparametric analysis. A statistically significant increase in the heat index was found in two of the three locations selected for this study. At the Phoenix Sky Harbor Airport (Phoenix, AZ) and Harry Reid International Airport (Las Vegas, NV) stations, seasonal maximum HI values exceeded the extreme danger threshold and seasonal average HI ranges were found within the dangerous range. The number of nonfatal occupational heat-related injuries/illnesses in Arizona, California, and Nevada were also analyzed and were found to be steadily increasing in all three states over the study period (2011-2018). The overall number of nonfatal occupational injuries/illnesses were also analyzed as a function of the length of service with the employer, which showed an increase in the number of events with an increase in the length of service. The time of the day and number of hours worked were also found to significantly affect the overall number of nonfatal occupational injuries/illnesses in the three locations studied. In addition, the number of days away from work after the occurrence of a heat-related, nonfatal occupational injury/illness event was significantly higher for events during which the worker remained away from work for more than 30 days. Results from this study suggest that extreme heat poses a real threat for outdoor workers and decision-making devoted to addressing this risk is required to prevent undesirable effects.