What is a fever temperature in children considered?

100.4 R : Most will consider the core temperature (rectal) the most accurate reflection of real body temperature. At 100.4 r, it has moved outside the accepted range for normal.

Fever- see doc?: When to see a doctor when your child has a fever? Depends on the age and how the child is doing: http://www.parenting.com/health-guide/fever/when-call-doctor