- Documented fever, defined as body temperature >38.0 ºC (100.4 ºF) taken orally; >38.5 ºC (101.2 ºF) tympanically; or >39.0 ºC (102.2 ºF) rectally or hypothermia, defined as core body temperature of <35.0 ºC (95.0 ºF)