If I lived any further south than North Carolina, my hiking season would be November through March. It's already plenty hot up here in the summer -- so I feel your pain.

I would take a light down 40-F rated sleeping bag. Make SURE it has a full zipper, so it can be opened and used as a quilt on the warmest nights. If you want to do any spring or fall trips, I would get a 30-F rated bag, which still works okay in the summer. If you want to do real winter trips, you need two bags, one for winter and one for the other three seasons.

Other than that, my advice is also in the other, similar thread. Good luck.