Fever in the middle of the night may be caused by respiratory tract infections, digestive system diseases, systemic infections and other factors. 1. Respiratory tract infections: for example, colds, acute tonsillitis, which can lead to fever in the middle of the night, may also be accompanied by coughing, phlegm, sneezing and other symptoms, the temperature rises are more pronounced, and in severe cases can lead to febrile convulsions (convulsions due to high fever). 2. Digestive system diseases: for example, acute gastroenteritis, acute appendicitis, etc., in the acute attack at night, will lead to fever in the middle of the night, may also be accompanied by nausea and vomiting, abdominal pain and diarrhea and other symptoms. 3. Systemic infectious diseases: toddler fever in the middle of the night may also be related to systemic infectious diseases, such as toddler emergency rash, chickenpox, hand, foot and mouth disease, the onset of more acute, more serious infection, will make the toddler fever in the middle of the night. Fever in the middle of the night may also be caused by non-infectious factors, such as Kawasaki disease, etc. Parents are advised to take their children to the doctor to avoid serious consequences.