yes, but the temps required to cause any changes to pool balls will never happen in the real world. and please all you in the peanut gallery don't start that 'but what about if you live on the n. pole' shit. other than the sweat you'll never see changes in how they play due to hot/cold.I spent many years working as a mold tech for an injection molding company.
One thing I can tell you is that temperature affects the size of any Phenolic resin item.
Objects made from phenolic resin expand as they heat up.
Billiard balls are made using a therosetting process that minimizes the contraction and expansion of billiard balls but does not totally eliminate it.
It is best to keep billiard balls at a controlled temperature for consistency.
Also, bringing balls in from cold temperatures will cause them to sweat which creates moisture on the surface.