A fever is a rise in body temperature reading above
A fever, or pyrexia, is a rise in internal body temperature to levels that are considered to be above normal. Average body temperature is about 98.6Â°F or 37Â°C, and temperatures above 100.4Â°F or 38Â°C are generally considered to be febrile. Body temperature is determined by the body's thermoregulatory set-point.