A core body temperature higher than 105 degrees Fahrenheit is a telltale symptom of heat stroke, says WebMD. Fainting is often the first visible sign of heat stroke.
Other symptoms of heat stroke include: headache, dizziness, nausea, vomiting, shallow or difficulty breathing, seizures, unconsciousness, and muscle weakness or cramps, according to WebMD. Some people suffering heat stroke have a rapid heartbeat, become unconscious or experience changes in behaviour, such as staggering, disorientation or confusion.
While heat stroke symptoms develop slowly in some people, others can develop symptoms quickly and without warning, reports MedicineNet.com. Severe cases of heat stroke may cause hallucinations, coma or death.