We define a fever as a temperature over 100.4 F (38.0 C). Normal body temperature is 98.6 F (37 C). Everyone’s body temperature varies throughout the day and can differ by age, activity level and other factors. Don’t be alarmed if your child’s temperature varies.
https://health.clevelandclinic.org/2015/05/kids-fevers-when-to-worry-when-to-relax/
1 Fevers may be your infant’s only response to a serious illness. 2  Your child’s fever lasts more than five days. We may need to investigate further for underlying causes.  Your child’s fever is higher than 104 F (> 40 C).
https://health.clevelandclinic.org/2015/05/kids-fevers-when-to-worry-when-to-relax/
1 An infant younger than 3 months of age develops a fever. Fevers may be your infant’s only response to a serious illness. 2  Your child’s fever lasts more than five days. We may need to investigate further for underlying causes.  Your child’s fever is higher than 104 F (> 40 C).
https://health.clevelandclinic.org/2015/05/kids-fevers-when-to-worry-when-to-relax/
1 Your child is younger than 3 months and has a fever. 2  Your child is age 3 to 6 months and has a temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable.  Your child is age 3 to 6 months and has a temperature higher than 102 F (38.9 C)
http://www.mayoclinic.org/first-aid/first-aid-fever/basics/ART-20056685
1 Your child is 2 to 17 years and has a temperature above 102 F (38.9 C) that lasts longer than three days or doesn't respond to medication.  An adult has a fever that doesn't respond to medication, is consistently 103 F (39.4 C) or higher, or lasts longer than three days.
http://www.mayoclinic.org/first-aid/first-aid-fever/basics/ART-20056685
1 Your child is 2 to 17 years and has a temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable.  Your child is 2 to 17 years and has a temperature above 102 F (38.9 C) that lasts longer than three days or doesn't respond to medication.
http://www.mayoclinic.org/first-aid/first-aid-fever/basics/ART-20056685
1 Temperatures of up to 102.5 F if your child is 3 months to 3 years of age, or up to 103 F if your child is older. These temperatures can be common, but not necessarily worrisome.  Low-grade fevers if your infant or child was recently immunized. These can be normal if they last less than 48 hours.
https://health.clevelandclinic.org/2015/05/kids-fevers-when-to-worry-when-to-relax/
Get medical help for a fever if: 1  Your child is younger than 3 months and has a fever. 2  Your child is age 3 to 6 months and has a temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable.  Your child is age 3 to 6 months and has a temperature higher than 102 F (38.9 C)
http://www.mayoclinic.org/first-aid/first-aid-fever/basics/ART-20056685
By Mayo Clinic Staff. A fever is a temporary increase in your body temperature, often due to an illness. Having a fever is a sign that something out of the ordinary is going on in your body. For an adult, a fever may be uncomfortable, but usually isn't a cause for concern unless it reaches 103 F (39.4 C) or higher. For infants and toddlers, a slightly elevated temperature may indicate a serious infection. Fevers generally go away within a few days.
http://www.mayoclinic.org/diseases-conditions/fever/basics/definition/CON-20019229
Get medical help for a fever if: 1  Your child is younger than 3 months and has a fever.  Your child is age 3 to 6 months and has a temperature up to 102 F (38.9 C) and seems unusually irritable, lethargic or uncomfortable.
http://www.mayoclinic.org/first-aid/first-aid-fever/basics/ART-20056685
what temperature is considered to be a fever
A temperature of over 100.4 Fahrenheit or 38.0 Celsius is considered to be a fever. 