A couple years back I did a fly-and-ride with just a carry-on backpack. Arrived in 85F Connecticut wearing rally/desert gear, picked up a vintage H-D lowrider with no windshield, and headed west.
Contrary to the 70-90F forecast, the first taste of winter came early. It was cool and occasionally wet in the midwest but I pressed on, warming up while getting food.
In Sturgis at last, the big H-D dealer had plenty of stock. I got a rainsuit, heavy waterproof gloves, and continued west on I-90.
WY, Montana, crossing the Rockies, and the Idaho panhandle were tough. The first breath of winter, 30-40F fierce headwind for 500 miles, slapping my beaked dual-sport helmet around. 65 mph top speed into the wind in 5th. Everyone (including semis) passing me doing 80 (that's Montana for ya). Approaching hypothermia, noticeable cognitive impairment.
Near Missoula the vintage fuel line let go. I stared at the liquid in a stupor - hey, my bike is not liquid cooled. Called my local buddy, barely able to form words at this point. He realized I was close to the H-D (multi-brand, really) dealer in Missoula, and I rolled in there dripping fuel.
Straight to the front of the queue in Service, a few hours and much coffee later, the fuel line replaced as best they could since it was a pre-formed line and of course not available, I continued to WA. Made it in one piece, didn't even get sick, quite an adventure.
But that H-D rainsuit over the ADV summer gear sure made the difference between impossibility and major suck.
Of course, it would have been nice to have been more prepared, and if I were on a tour on my GS, I'd have the kitchen sink along. But this bike had no luggage provisions and nowhere decent to strap anything down, and I had just the one carry-on, so no tools of any kind either.
In sum, almost anything is doable with a bit of grit and determination. I wouldn't stress about a half hour 50F commute.
As someone mentioned, bicycle gear has some amazing options. I have skin-tight single layer Assos and Castelli windproof, waterproof gear that's good for 25F fat biking on (optionally) studded tires around here. Something like an intermediate weather bicycle layer under a riding jacket may well do the trick for that terrible Bay Area winter.