A temperature of 97.3°F (36.3°C) is within the normal range for a baby. Normal body temperature for infants generally falls between 97°F and 100.3°F (36.1°C to 37.9°C), depending on how and when the reading is taken. A fever in babies is defined as a rectal temperature of 100.4°F (38°C) or higher, so 97.3°F sits comfortably below that threshold.
Why 97.3°F Falls in the Normal Range
Many parents expect a baby’s temperature to land right at 98.6°F, but that number is just an average. Healthy babies routinely register anywhere from the high 96s to just over 100°F throughout a normal day. Body temperature fluctuates based on the time of day (it tends to be lowest in the early morning and highest in the late afternoon), how recently the baby ate, how active the baby has been, and what the baby is wearing.
A reading of 97.3°F simply means your baby is on the lower side of that normal window. This is especially common during sleep or right after a nap, when metabolic activity dips and body temperature naturally drops.
How the Measurement Method Affects the Number
Where you take the temperature matters. Rectal readings are considered the most accurate for babies under three months old, and they tend to run slightly higher than readings from other sites. Armpit (axillary) readings typically come in about 0.5 to 1°F lower than rectal readings, so a 97.3°F armpit reading could actually reflect a core temperature closer to 98°F.
Forehead and ear thermometers are convenient, but research from the Canadian Agency for Drugs and Technologies in Health found that rectal and axillary readings cannot be used interchangeably, and that forehead and ear thermometers are less reliable substitutes. If you’re getting a reading that concerns you, a rectal measurement gives you the most trustworthy number for a young baby.
When a Low Temperature Is Worth Watching
While 97.3°F is normal, there is a point where a low reading signals a problem. A rectal temperature below 96.8°F (36°C) in a newborn can indicate the baby is having trouble staying warm, particularly in the first few weeks of life. Premature babies and very small newborns are especially vulnerable because they have less body fat for insulation and a larger skin surface area relative to their weight, which means they lose heat faster.
The CDC notes that babies experiencing true hypothermia show bright red, cold skin and very low energy. If your baby’s temperature drops below 97°F on a rectal reading and the baby seems unusually sleepy, feeds poorly, or feels cool to the touch on the chest or belly, those signs together deserve prompt attention. A single reading of 97.3°F without any of those symptoms is not a cause for concern.
Babies and Temperature Regulation
Newborns are not great at regulating their own body temperature. They can’t shiver effectively to generate warmth, and they lose heat quickly through their heads and skin. This is why hospitals keep newborns skin-to-skin or swaddled immediately after birth. Full-term, healthy babies develop more reliable temperature control over the first several weeks, but in those early days, their readings can swing a bit more than an older child’s would.
By around three to four months, most healthy babies maintain a more stable temperature on their own. Until then, the environment plays a bigger role in what the thermometer shows.
Keeping Your Baby at a Comfortable Temperature
The room where your baby sleeps has a direct effect on their body temperature. The Lullaby Trust recommends keeping the room between 61°F and 68°F (16°C to 20°C), paired with light bedding or a lightweight sleep sack. Staying within this range also helps lower the risk of sudden infant death syndrome (SIDS).
A good rule of thumb: dress your baby in one more layer than you’d wear comfortably in the same room. If you’re comfortable in a t-shirt, your baby likely needs a onesie plus a light sleep sack. Overdressing a baby is actually more common and more dangerous than underdressing, since overheating is a known SIDS risk factor.
If your baby’s temperature consistently reads on the low side, check that the room isn’t too cool, that the baby’s hands and feet aren’t exposed for long periods, and that you’re getting a good reading with proper thermometer placement. A warm baby with a 97.3°F armpit reading is almost certainly fine. A cold, lethargic baby with the same reading warrants a rectal check and closer monitoring.