I was out the other day in similar air/water temps - it was blowing a good 15+mph steady with decent chop.
With that wind speed and chop, you will be wet and wet + wind = cold. Even though the sun was beating down on me it wasn't long (15-20 min) before I chilled.
I bought a set of Frogg Toggs a few years ago for camping - they are very light weight and pretty cheap. Since they weren't being used much for camping trips I decided to try them out for sailing.
They work pretty well !! They store in their own ditty bag and pack up into a small package, weigh next to nothing and they're easy to put on - in the above scene, all I did was reef the sail, reach into the hatch and I had them on in less than a couple minutes and was on my way.
They are NOT a dry suit by any means but they work better than I expected in keeping the spray off me without me feeling like I was wrapped in a plastic bag. Sure, alittle water gets in the elastic wrist/ankle bands but in 80+ degree heat thats not a problem
For ~$50 its a good thing to have stored aboardhttp://www.froggtoggs.com/store/outerwe ... it-10.html
This is the set I have