My average is a little lower than yours at the peak of the season, about 15.5. Right now, I am happy if I average 13. Riding in the cold is a whole other thing. The cold doesn't bother my asthma, but after I get dressed like marshmallow woman and take a half hour to get ready to actually go out in cold temperatures, it takes a lot more effort. Especially with wind. Be happy you are still out there, riding.
Take your inhaler before you ride and don't breathe through your mouth!