When he gets really hot, try taking a bath with him in tepid water. Works well for us. He'll hate it, but the payoff is worth it for him.
Could he have Roseola?
http://kidshealth.org/parent/infecti...n/roseola.html
Starts with 4 days of bad fever, then becomes a rash for about one day.
Kinda like a mini case of the measles. Our guy had it last month.