I don’t know if this helps, but I did a century in the rain a couple of weeks ago, and I just dressed normally(Short sleeve jersey and shorts). It was similar weather to what you describe, and if I had worn rain gear I would have been too hot. As it was, I was soaked after the ride, but more comfortable than if I had worn rain gear.
One thing you should definitely do is cover your saddle and running shoes so that they are at least dry when you put them on.
See you there and good luck. I haven’t decided what to bring but in the end I’ll probably just wear what I wear when it’s nice and be cold on the bike. I over heat and sweat like crazy normally. You could also try some skin shield cream but I don’t know if the wet suit would rub it all off. Hopefully the water is warmer than Lake Washington which was brutally cold last weekend. If you’re in the 35-39 AG, I would suggest you wear something big, heavy and baggy;)
I hear you, man. 3 weeks ago was the last time I hit Lake WA and I got lucky with a supposed 58-60F water temp. The following weekend, somebody I swim with got hypothermic… the race website sez the H2O temp is mid 60’s, but I am not buying it…
anyhow-good luck to you as well. I am a couple waves ahead of you, M30-34. thanks for the suggestion on the attire. do you have a race #? i don’t know mine off the top of my head. good luck with the drive down too.