Normal axillary temperature, which is taken under the arm with the arm snugly against the body, ranges from 97.5 to 99.3 degrees Fahrenheit for infants, according to Sutter Health. Normal rectal temperatures are less than 100.2 degrees Fahrenheit.
Babies should have their temperatures checked when they appear sick, but they do not need to have their temperatures checked on a regular basis. Indications that a baby might be sick include increased irritability, hot skin, sweating, development of a rash, unusual breathing and poor appetite. Electronic digital thermometers are recommended for accuracy, states Sutter Health. Ear thermometers should not be used with infants younger than six months old.