As a child (Italy) I was taught that the temperature measured outside the body (armpit) would be usually 0.5C lower than the one measure inside the body (rectum

As a child (Italy) I was taught that the temperature measured outside the body (armpit) would be usually 0.5C lower than the one measure inside the body (rectum, mouth). The threshold for "fever" as reported on all old mercury-based thermometers was exactly 37C and that was referring to the "inside" termperature. So 36.6 outside would definitely be considered onset of mild fever, not normal. 36.6 inside would be a-ok