The hairs on Xander's arms just started lying flat against his skin. Which is most likely his internal body temperature?

This condition states that Xander's body temperature is normal. The human feels a little warm. It is due to the various metabolic activities that takes place inside human body.

Not everyone has the same body temperature. The normal body temperature is 38°C. But this can be a bit higher in case of children.

The temperature of the human does not stays same all day. It varies according to the work you do and the time of the day.