My DS is exactly like this. In the middle of winter I couldn't wrap him in anything heavier than a light muslin or he would overheat. Now he sleeps in a sleeping bag which makes things easier to control his temp. He has a sleeveless one which also keeps him a bit cooler and they come in different weights for different times of the year. We also have a fan and an air conditioner in his room. Getting his room cool before he goes to sleep is also a good idea.