Yes, if you BO in kp rib the edge stays right on the edge. When you BO in purl, the edge will be on the other side. I often BO in purl on the RS to make a little garter ridge.
Hah, never trust the forecast. You'll have enough humidity in your location to make it uncomfortable. It's bad enough here with 12% humidity and 85 or 90.
sue- knitting heretic