I just spent a week hunting at below zero temps. I was only out for 30-40min at a time so YMMV.
My safety got super stiff and my magazine didn't always advance on my BRK Sniper, other than that it worked fine. I didn't have either issue with my Avenger or Notos, go figure.
With all 3 my POI might be down a fraction, but not so much it made a difference on my Crosman squirrel targets I use to unload before heading inside.
Long term it might mean I'm replacing o-rings sooner, we'll see...
Regardless, I'm still going to go out no matter the weather.