Heat stroke is also known as hyperthermia. It is a condition that occurs when the body becomes overheated as a result of being exposed to high temperatures for a long period of time. More specifically, heat stroke occurs when your internal body temperature is greater than 104 degrees Fahrenheit. Simply being in the sun/hot weather for a long time can cause heat stroke. Some people may think heat stroke can be taken lightly, but it is actually a medical emergency and requires immediate treatment. About 334 people in the United States die each year from heatstroke.