How many degrees celsius and farenheit is considered a fever in children?

Fever: Fever is a body temperature of 100 f or higher.

Depends on age: In young infants up to a month of age anything above 38 degrees celsius or 100.4 degrees fahrenheit via rectal temp is considered a fever. In a child from one month of age and above, fever is anything above 38.2 celsius or 100.7 fahrenheit.

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