I find that it is fine when consistently below zero, even with snow piled up next to roads, the roads are dry and ice free. biggest issue is warm days and cold nights as roads can get icy. Been caught in falling snow a couple of times on the road bike, which is a bit dicey. Even so I try to ride to work once per week on average over the winter, and saturday club ride was only cancelled once.
Mountain bike on Zugerberg in snow is great fun… cycling with the cross country skiiers
I don’t mind absolute brass monkeys below zero stuff if it’s dry with just ice or snow on the ground. It’s the wet, 4C all day and low light stuff that I find hard work.
My trusty DHB one is coming to end of life. The newer DHB merino ones don’t seem to be as warm; and despite my pea sized head - they feel quite tight when sunnies on under it.