Cause of febrile seizure
There's no specific temperature that causes a febrile seizure. Rather, it's a drastic change in temperature. It could be a normal temperature suddenly spiking to a low fever (101) or it could be a fever suddenly going away that could cause them. In general, if your child has one febrile seizure doctors will tell you not to worry but to be sure you are keeping them hydrated and are watching over them (call your doctor anyway though, I am NOT a medical professional). If a child has a second febrile seizure, it is usually suggested to take them to the ER to find out what is causing the drastic temperature changes.