How would you dress for the bike in a half ironman - like Ralph’s California? Temperature - low 60’s, off and on heavy rain (not just sprinkles). Rain jacket? Glasses? Leg warmers? Arm warmers?
Dont want to sound like a jerk but how did you dress when you trained in those conditions? (unless you live in a desert like area somewhere) Thats the way you should dress.
Regular one or two piece tri-suit, then arm-warmers, maybe knee-warmers, and a tight fitting full zip wind vest and gloves. I would also use the neoprene toe warmers on my shoes. It may take an extra 30 sec to pull on thr extra gear in T1, but it would be well worth it.
Fleck
Standard tri bike kit, plus knee warmers and arm warmers (you can put on the knee warmers and swim with them under your wetsuit). Either shoe covers or put your toes into plastic sandwich baggies before putting on shoes. Rain-resistant windproof vest with full zipper. This setup is warm enough for a San Diego winter storm, yet allows you to strip off the arm warmers and vest on the fly if it gets too warm (which it often does, even on blustery days).
Gosh…is that pretty much what Fleck already said…? 
I always race the bike with clear lenses in my M-frames. I switch to real shades for the run (if needed). No hat, especially if it rains.
A cycling cap is a good way to prevent drip from the helmet into your lenses.