Running a fever

Ds woke up from his nap around 5. I noticed he was a little warm and thought it was from him just waking up. About 20 minutes ago I took his temp and it's 103.2. He isn't presenting any signs of coming down with something. We live in NY and it was 87 degrees today. We were outside for a bit but I've made sure to keep him hydrated. He has hirshsprungs disease but he isn't presenting any signs that he could be having problems with that either. He has a fan in his room plus I've had the AC on. If my kids run a fever it's because they are actually sick with something. This is the first time this has happened. Help please!