It may be a little cold outside and the sun goes down at like 5pm but, there is no snow and no ice on the ground! That makes for prime riding weather. The only issues become staying warm and how long you can handle the cold for. I got out for a 2 hour fixie ride last night just around town and I was okay till I stopped an hour and a half in for a nature break then I got cold. My second water bottle was mostly frozen like an icee at that point, I've found that hot water is good for about 1 to 2 hours at 20 degrees. I'm thinking of taking the fixie out again tonight and skipping on the dirt after taking a hard fall on j11 sunday it might be time to spin easy on some pavement anyway.
Oh ya, I love the dirt drops (Origin 8 Gary bar) on the fixie!