Bowling balls in high temperatures will soften; this creates extra hook. Also, when the weather is warm outside, your hand will swell, making the finger and thumb holes in the bowling ball feel tight. If the bowling center is air-conditioned, your hand and bowling ball will adjust to the cooler air.
The opposite is true of cold weather. The harder ball will skid more and hook less in the winter, and your hand will shrink in the cold and swell back to normal inside.
The best solution is to simply bring bowling balls inside after you come home from the bowling alley and wait until the last minute to put them in the trunk again. If you must leave for bowling directly from work, try to put your equipment in the trunk that morning and arrive at the center early to give the bowling balls and your hand time to acclimate. Not doing so could lead to cracking or core separation not covered by manufacturer's warranty.