A fever is an overall increase in body temperature that is above the normal 36°C to 37.5°C (96.8°F to 99.5°F) range. Most commonly, fever is a symptom of an infection and might indicate that you have a cold or the flu.
Because children's immune systems haven't had a chance to fully develop, they are more likely to get infections. Also, frequent exposure to other children can increase chances of picking up an infection. This is a normal part of childhood and prepares the immune system for the rest of the child's life.