Night Sweats? Keeping me awake.?

My husband is soooooooooo freaking hot at night! I don't understand. We sleep with a fan and window open. He's not overweight and is hot before I even get in bed. (he goes to bed first usually) It's really starting to get uncomfortable and keeps me up because I'm now hot and sweaty. We both sleep naked to and under a sheet and light blanket. What's going on?