I grew up in North Dakota, and had several outside blue collar jobs in the winter. I've only lived in So Cal for 5 years. My personal record was -50 F without windchill, and I've seen -20 F many many times.
One of my favorite memories was a cold spell in Jan in Bismarck when it never got above 0 F for 20 consecutive days, I stepped out of my front door, took a deep breath and the inside of my nose froze and immediately started bleeding, and forming bloodcicles on my mustache...
I don't recall ever wearing or seeing anyone else wear their watches where they were exposed to the cold for more than a few minutes at a time, particularly metal watches, LCD watches would stop working around 0 F, and have to warm up before working again, LED watches tolerated temperature extremes a lot better.
Cold is really the absence of heat, and a metal Apple watch will conduct the heat of the user to the ambient air, never dipping below 32 F unless the circumstances were extreme, in which case a watch that was 32 F or lower would cause tissue damage and you would have taken it off prior to it getting that cold because of the discomfort, or you're a corpse and your heat has radiated away from your body.
And for the record, I really am Steve's love child, or Tim's partner, I can never keep that stuff straight...