A temperature of 98°F is not a fever for a child. In fact, it falls comfortably within the normal range. A fever in children is defined as 100.4°F or higher when measured rectally, in the ear, or with a temporal artery thermometer. For oral readings, the threshold is 100°F, and for armpit readings, it’s 99°F.
If your child’s thermometer reads 98°F and they seem unwell, the number itself isn’t the concern. Here’s what actually matters.
Why 98°F Is Completely Normal
The old idea that 98.6°F is the “correct” body temperature dates back to the 1800s, when a German physician averaged armpit readings from about 25,000 people. Modern research tells a different story. An analysis of 20 studies published between 1935 and 1999 found the average oral temperature was actually 97.5°F. A more recent 2023 study of over 35,000 people put the average at 97.9°F. Over the roughly 160 years of data analyzed, average body temperature gradually dropped by more than a full degree.
So 98°F isn’t just “not a fever.” For many children, it’s right around their personal baseline, or even slightly above their resting norm. A healthy child’s temperature can sit anywhere from about 97.4°F in the morning to 99.6°F in the late afternoon. That nearly two-degree swing over the course of a day is completely normal and driven by the body’s internal clock.
What Actually Counts as a Fever
The threshold depends on where you take the temperature, because different body sites run at slightly different readings:
- Rectal, ear, or forehead (temporal artery): 100.4°F or higher
- Oral (under the tongue): 100°F or higher
- Armpit (axillary): 99°F or higher
Armpit readings tend to run lower than core body temperature, which is why the cutoff is lower. Rectal readings are the most accurate for infants and young children because they reflect internal temperature most closely. If you’re getting a reading of 98°F from any of these sites, your child does not have a fever by any medical definition.
Readings Between 99°F and 100.3°F
If your child’s temperature creeps into the upper 99s, that’s sometimes called a “low-grade” elevation, but it still doesn’t meet the clinical definition of a fever when measured orally. Temperatures in this range can be caused by things that have nothing to do with illness: running around, wearing heavy clothing, sitting in a warm room, or simply being checked in the late afternoon when body temperature naturally peaks. If you suspect environmental factors pushed the reading up, let your child rest in a comfortable room for 15 to 20 minutes and check again.
When to Worry Without a Fever
A normal temperature doesn’t automatically mean everything is fine. Young children can be sick without running a fever, and their behavior often tells you more than the thermometer. Signs worth paying attention to include:
- Unusual tiredness or difficulty waking up
- Feeding poorly or refusing fluids
- Breathing faster or harder than normal
- Persistent crying that doesn’t improve with comfort
- A new rash
- Pale or yellowish skin
- Vomiting beyond normal spit-up
Any of these symptoms deserve attention regardless of what the thermometer says. A child who reads 98°F but seems limp, won’t eat, and can’t be consoled is more concerning than a child who reads 101°F but is still playing and drinking normally.
A Note About Infants Under 2 Months
For very young infants (8 to 60 days old), the rules are stricter. A rectal temperature of 100.4°F or higher in this age group warrants prompt medical evaluation, even if the baby looks well. The American Academy of Pediatrics has specific guidelines for these young infants because their immune systems are still developing and infections can progress quickly. At 98°F, this doesn’t apply, but it’s useful context if your newborn’s temperature is climbing and you’re monitoring it.
Getting an Accurate Reading
If you’re rechecking because your child feels warm to the touch but the thermometer says 98°F, the thermometer is more reliable than your hand. Skin can feel warm after physical activity, crying, or being bundled up. To get the most accurate reading, use a rectal thermometer for children under 3 and an oral or temporal artery thermometer for older kids. Avoid checking right after a bath, a meal, or heavy play, all of which can temporarily shift the number in either direction.
A reading of 98°F, taken correctly, is a reassuring number. If your child is acting like themselves, eating, drinking, and engaging normally, there’s no temperature-related reason for concern.