What is a primary symptom of heat stroke when working in extreme heat?

A primary symptom of heat stroke is the lack of sweating, which occurs when the body is unable to cool itself down effectively due to extreme heat exposure. In a typical response to high temperatures, the body sweats to facilitate evaporative cooling. However, during heat stroke, the body's thermoregulation fails, leading to an inability to produce sweat despite a significant rise in body temperature. This condition signifies critical failure of the body's heat regulation systems and can lead to serious health complications.

While excessive sweating is often associated with heat exhaustion, shivering and nausea are not primary symptoms of heat stroke. Shivering typically indicates the body is attempting to generate heat instead of dissipating it, which is counterintuitive in the context of heat-related illnesses. Nausea can occur with many conditions, including heat-related ones, but it is not as definitive as the absence of sweating in identifying heat stroke.