A fever is usually caused by infections from viruses (such as a cold or the flu) or bacteria (such as strep throat or some ear infections). The fever itself is not the disease, only a sign that the body’s defenses are trying to fight an infection.
Your child's normal temperature will vary with his or her age, activity, and the time of day. Infants tend to have higher temperatures than older children, and everyone's temperature is highest between late afternoon and early evening and lowest between midnight and early morning. Learn more here.