I went out this morning to the course and the temps were in the mid to high 40's with a rather steady easterly wind. I had on my performance base (thermal) and my short sleeve Dry Joys Tour Collection rain shirt.
Initially, I thought I would be cold, but had absolutely no problem at all. The thermal base performed flawlessly! I am happy to have the black and the white versions in my collection (see below).
If you are considering purchasing a Performance Base, my recommendation is to go and do it! You will not be disappointed!