Low humidity would speed things up a bit. Air condtioning should neutralize any differences you see in ball speed.
I remember a time while playing at the Cue Club in Las Vegas where the players could actually sense a difference in ball speed when the front door was propped open. Considering how big the room is, I thought that was amazing.
A/C has very very little effect on humidity, cold is not wet air. Vegas is dry all the time, cold or hot.:smile:
Dry=fast