There are many factors that can negatively impact worker safety in manufacturing or industry. In particular, hazards such as contact of workers' hands or other body parts with overheated components can lead to accidents and production losses. Hot surfaces cannot be seen with the naked eye. To detect hot surfaces, thermal cameras can be utilized in work areas. Placing multiple thermal cameras in large work environments, such as factories, is cost prohibitive, and carrying them is not a solution. This paper proposes an augmented reality-based assistant that visualizes hot surfaces by integrating thermal camera information into augmented reality goggles. The major advantages of the system are twofold: (1) it consists of an untethered mobile hardware platform with a thermal camera that can send information through a wireless connection, (2) the visualization is implemented for augmented reality head-mounted displays that do not require the use of workers' hands, unlike tablet-based augmented reality. Augmenting human sight with thermal vision may also have an impact on other research areas in the future.