What Causes Child To Have High Fever At Night?

Good Morning! My grand daughter is 5, at night she spikes a fever - sometimes as high as 104 or the other night was 107. She isn t sleeping well due to nightmares which I am assuming are due to the fever being so high. During the day, she is tired (likely due to no real sleep) but there are no real other symptoms. She sometimes has a headache, which we attributed to the fact that she won t wear her reading glasses at school. Her appetite is fine, almost to the point of growth spurt time. During the day her temperature is usually between 98 and 100 so no real spike there. Any ideas? This poor little one needs to get some sleep.