Upstate NY. We only get below 0F about ten nights and two days per year. There are mountains in California, so there might be a small percentage of its population that actually know what winter is... but anyone in Kentucky, Virginia... sheesh.
Bontrager RXL Convertible 180 is what I use. Thin merino base + mid/heavy merino Icebreaker or Surly midlayer + pedaling somewhat hard and I’m good down to -15F. With a thin poly jersey it’s useless above 30 unless I zip off the sleeves.
It’s less fragile than some cycling stuff I’ve got, but you still need to be kinda respectful toward it.
i think I’ve got four winters with it- 70-130 mile weeks- threads are starting to pull out here and there. I probably could get a fifth season out of it if I had to.