An electronic device comprises an enclosure configured for insertion into the ear canal and comprising a distal end configured to extend at least beyond a first bend of the ear canal. A distal temperature sensor is situated at a location of the enclosure that faces a tragus-side of the ear canal between the first and second bends when the enclosure is fully inserted into the ear canal. A proximal temperature sensor is situated on the enclosure at a location spaced apart from a surface of the ear canal and proximal of the distal temperature sensor in an outer ear direction when the enclosure is fully inserted into the ear canal. A processor, coupled to the distal and proximal temperature sensors and to memory, is configured to calculate an absolute core body temperature using a heat balance equation stored in the memory and the first and second temperature signals.