I motorcycle commuted in my 20s, had a snowmobile suit and a full helmet/face shield and in dry conditions, I was pretty comfy on the way in when it was in the low 20s. Any chance of ice (or those mornings where lots of people are driving around with tiny viewing ports scraped into their windshields instead of waiting for the defroster to do its thing...) and I wasn't on the motorcycle.
Bike commuting in my 30s and early 40s, below 30 it just wasn't fun and had the same rule about any ice possibilities.
Now, recreational riding below 40f is just not fun - it is always in the 50s or 60s in the basement where I can wimp out and ride on trainer/Zwift!