I have 2 Leica F ( black III , 1933) cameras and one D (black II, 1932).
I don't believe I have taken the F's out in cold weather.
I did take the D out to shoot a "Santa train" the other year, weather was clear and cold, with temps hovering around 5- 10 deg F, with a stiff breeze.
After being outside for an hour or so, the shutter began to drag.
As far as I know, the D had not been serviced since leaving the factory.
It works okay in warm weather.
My daily shooter is a 1934 Leica III, that does not seem to mind the cold one bit.
I think that camera has had at least one CLA since leaving Wetzlar.
I have a technique for checking cameras for cold sensitivity - I put the camera in a new zip-loc freezer bag, with some silica gel, and put it in the refrigerator overnight. Next day, I will pull it out and run it through the range of speeds (starting at fastest) while still in the bag. If things are gummy due to cold, it will usually show-up by the time I get down to 1/100 to 1/50.
I've discovered quite a few warm-weather pikers this way. Not a very scientific method, but if a camera goes sluggish at 35-40 F in the Fridge, I would expect worse out in the wilds.
My trusty Pentax SP-500 Spotmatic just started acting-up in the cold.... after being outdoors for a while at 40 F, the mirror stopped returning at speeds below 1/100... I assume that means the shutter isn't closing either... so I need to get that beast out for a CLA.
One other thing about Leicas / Nikon RF in the cold: a gloved "shutter finger" will usually drag on the speed-dial when you release the shutter, wrecking the exposure timing.
My Contax IIIa shutter starts "capping" at 50 F, and stops working all-together at 30-35 F.
Good luck !
Luddite Frank