D.C.
My daugher sweats like crazy, too! I switched from the warm, fuzzy pjs to light, cotton ones, and that seemed to help. She did not care to be swaddled, so that also eliminated a layer. If you believe he's really too warm, you might want to skip the onesie underneath the pjs, if you're using them. Also, I asked my pediatrician if I should be concerened about her overheating during the night and sweating too much, and he said it's not a concern. But I would ask your doctor, too, just to get another opinion.