I think you are right that an extreme cold-warm temp change would be bad. Assuming you or someone had accidentally left your stuff in the car, I would take it out, and leave the balls to set out at room temperature and wait the hour or 2 before it felt warm to the touch again. I would not run hot water or even warm water over the ball to get the ball warm again.
If you were in a situation where you absolutely had to keep your stuff in the car during some bitter cold, I would get a bunch of blankets or something to insulate, and wrap them around your bowling bag. This should keep most of the extreme cold from getting thru, and should lessen the time it takes to get them to room temperature.
OK, this was about the hardest post I have ever typed. Every sentence I had to keep re-editing because it just came out wrong. My mind is gone today
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D <~~~~ Used to be terrible wiffing 10 pins. Now through much practice, can wiff any single pin spare at any time.
Darrell Guzman
guzmand19 - Yahoo IM and MSN screen names