Warm weather, I just get wet with my regular cycling clothes. Feels good actually. When it's colder, say in the 40's, I'll generally wear a water resistant windbreaker and shorts, possibly with water resistant warmup sweats. Forget about aero, I'm just making the trip in those conditions.

Now I have my windshield fairing, so I was bone-dry after the rain on Friday . It doesn't matter what I wear in that case.