To me it’s dumb to leave a battery outside in the winter unless it’s on a daily driver.
My boat battery and battery for my Dart sit inside during the winter, at room temp.
Hit them with my little 1.5 amp battery tender couple or 3 days before I intend to use them to top them off at 100%, then put them in the car/ boat .
Both have been in use over 5 years now, still perform like new
In fact, gonna put boat battery on tender today, getting boat in the water Saturday, we have had frost here too recently( Mi)