Does anybody know around what temp the balls normally crack...
I have heard stories of balls cracking in houses and I know that cant be the reason...
Will anything lower than 30 crack a ball --- YES I AM LAZY AND DONT LIKE BRING THE BALLS IN THE HOUSE... YOU NEVER KNOW WHEN YOU MIGHT NEED THEM...

I used to leave mine in the car in michigan.  Never personally had issues with cracking.  All single drills.  that being said, it is dangerous to the equipment.  also, found my shoes sticky and my finger and thumb holes rather uncomfortable with the condensation with cold items in a warm environment.

If you are lazy just leave them in the car. It doesn't really matter.

Just from my own personal experience, the problem isn't so much that they reach those temperatures, its that they reach those temperatures and then you bring them into a much warmer or cooler climate and then immediately toss one.

I left an El Nino 2000, Storm Eraser, and a Columbia 300 Beast all in my parents barn for 3-4 years, brought them in, let them warm to room temperature and had zero problems.

The core, filler and shell are all made of different materials and will have different expansion/contraction rates so if you take them from extreme cold to extreme warm you are probably just increasing the chances that it will crack.

As far as working in the industry over the years, I only notice issues with heat not so much with cold temps. so leaving them in your trunk during the summer in Phoenix is really bad compared to leaving then in your trunk over the winter is typically not as much of an issue. The thinner the coverstock has a lot to do with it also. Defiant souls crack a lot. Hyroads not so much