Upper 50sF. It's comfortable, but we haven't really had a summer yet.

I left 5 minutes early, and wound up catching and passing 4 other cyclists. Usually I'm lucky if I even see a cyclist. I also reeled in a commuter-roadie (with small panniers) but didn't pass as he was cruising around 17 and that was comfortable.

One guy I caught on a hill. Squeaky chain and all. I want to carry a bottle of lube around for mandatory de-squeaking stops.