Nearly half of all frontline workers, such as firefighters, construction crews, and utility personnel, perform their jobs in outdoor environments where they face extreme heat or cold conditions. Exposure to extreme hot and cold temperature environments has caused many workers discomfort and illness from the exertion of thermal stresses on the body. Current methods for measuring core body temperature are either invasive, expensive, or less reliable, as the data algorithms used in existing models do not account for all worker types.