The ride was more difficult in some ways that I thought it might be. There was definitely humidity in the air when I left but it really wasn't foggy. Heading down 2A towards Concord, it turned foggy then really foggy. There weren't many cars on the road and I turned to let the ones I did see know I was there (my very bright light was mounted on my helmet) so I didn't feel unsafe. The worse conditions were at the low point on 2A just east of the intersection with Lexington Road but got much better by Concord center. The fog conditions never got quite as bad as that stretch during the rest of the ride but it was never what you could call clear either. I stopped to snap a picture from the Maple Street bridge. A few minutes later a small peloton (about 12 people) came towards me in the opposite direction. There were well lit like I was and quite visible, making me think I wasn't quite so dumb for being out there in the foggy conditions. It turned into a very nice day after the ride.
Fog from the Maple Street bridge, a couple of minutes before I saw the peloton: