Weather pred. for sunday's sprint is 47 degrees and rainy

Last year I asked a very similar question. Turned out to be 33 degrees at race start. I could see my breath. I wore shorty john wetsuit over tri shorts and sports bra in the water, threw on a dry short-sleeved running shirt and light bike jacket in T1, and by the time T2 hit, I peeled off the jacket. I think it topped out at 47 that day.

In other words - you'll be fine.

One thing I didn't do last year, but did do this year and I'm so glad I did, was put on some wool bike socks in T1. It's much nicer when you can actually feel your feet on the run. 

I'll take that over the 97F we had last sunday.

I did a sprint this past Sunday and it was in the mid 50s.  I just decided to suck it up in my tri shorts and tank.   I would have liked to have been warmer, but by no means was I shivering (well, after a few miles on the bike) and I can't say it affected my time.  I saw many people who put on a jacket or something on the bike.  I chose not to and don't regret my decision.    That said, it was sunny and it warmed up to 80 a few hours after the race was over.  

One thing I will say... it took a few miles for me to be able to see out of my sunglasses on the bike.   They got all dewey in transition while I was swimming.   I couldn't wear them for a while.  Had to have them on my head, kept them in my mouth, put them low on my nose so I could watch them and see when they were clear.   But if you're expecting rain maybe you won't be wearing sunglasses anyway.

Yeah, but that was humid as all get out!   NASTY!