Since we all know that golf balls in colder weather don't travel as far as those in warmer weather, it makes sense to maximize the distance potential of our golf balls however possible, but within the rules. I have a legal trick I use to play warmer golf balls than I might normally have just pulling them from the bag. Obviously, don't leave golf balls in the trunk of your car in the bag overnight before your round.
What I do is take a handful of ProV1x balls and roll them up in an electric heating pad about 1/2 hour before leaving for the course to get them all good and warm. Then as I walk out the door, I unplug the pad and leave the balls all wrapped up in it, then place the whole pad into the insulated section of my Titleist Lightweight Cart Bag. (Most other brand bags come with insulated sections these days too, I think.) Though I have altered the state of my equipment, I didn't do so during the round, and the alteration was not to any non-conforming spec, but just back to the specs the ball carried in normal summer weather. When I get to the course on that 45 degree day, I reach into the insulated compartment, through the heating pad and pull out a nice toasty ProV1x to tee off with. The others continue to slowly cool down, but frankly, it takes nearly the whole round to lose all the heat that was pumped into them hours earlier.
I know many who play ladies golf balls when it gets cold to get a few more yards, but I don't really like that idea. If you have been playing a ProV1 or x and have gotten to expect certain characteristics from the ball, a ladies Precept is going to gain you nothing. WIth a warm ProV you will get better distance off the tee. And, though, it may be a little harder to do a "one hop and stop" from 130 out with the harder surface conditions in cold weather, the spin you'll get from around the green will be much more than it would be with a lesser ball of any type/brand, no matter how warm you make it.