I rode the other day at 18F, but that’s about my low limit. With the right gear you can be quite comfortable. I would take 20* over 100* any day.

I hate cold weather.
I also work in a town about 35 miles from where I live and since I also take my kids to school in the morning I don't have time to commute by bike. On the other hand, I do keep a bike on the college campus where I work and ride it at least a couple of miles a day to and from the parking lot and around campus for meetings, etc.
Yesterday it was 15°, but with 25 mph winds. This morning it was 18°, but with much lighter winds. I don't like it, but for such short distances I'll ride in it anyway.

Tonight I set a temp record, it’s 0f with no wind. A 30min wasnt too bad until I came inside and realized how cold my toes were.

Still, way better than being bored to insanity going nowhere on a trainer. :)

No car. (by choice.)
No public transportation here.
No funds for a cab.
No friends or acquaintances to bum a ride from.
Nothing is within "walking distance" of where I live. (Plus it is too daRn cold out to walk anywhere.)
Therefore, I ride my bike or trike everywhere, year round.

Love my car and truck.
Cold doesn't bother me as I can dress for it, but no way I'm getting hurt by falling on ice. Waiting for safe conditions.

I dont like glare (black) ice, either. Being a snowrider on pavement and gravel at the mercy of road crews, I am continually relieved and surprised to find the surfaces quite acceptable for my mountain bike and 1.95” tires. So far, so good. No falls and the limited traffic around me has been safe.

Yes, but in Watopia.

Honestly, the roads around here aren't safe due to ice. I'll stay on the trainer for a while.

A wonderful bright sunny, almost windless day. A light coating of snow on the mostly unplowed dirt roads helped with traction over the icy spots. Temp started out at -15, then mid day touched on zero. Went for a great ride. Afterward sat on the deck in a sun drenched rocking chair and sipped a grapefruit Radler - it started to get a little slushy before I finished it. One can get suprisingly parched riding in cold weather.