Much depends on the way the locks are oiled. Too much of lube, or the lube which goes solid at the temp, and you might have dry fires. Age doesn't have anything to do with that.
On the contrary, in real freezing cold, say below -25 C., I'd much rather be shooting a hammer gun than a modern semi - if it does have lube problems, you've been had for the day, while a dry fire in a hammer gun is easily checked by re-cocking the hammer and having another go. Most shells which won't fire due to weak lock will go off the second time.
Ammo, as noted above, is affected too. Basically, when it's real cold, most plastic wads have problems, either with breaking in the barrel or, most commonly, with obturation problems due to being too stiff. Fast powder and fiber wads (felt is best) are the way to go.
